diff --git a/icu4c/source/common/convert.cpp b/icu4c/source/common/convert.cpp
index 63a036dc28..f359196b7a 100644
--- a/icu4c/source/common/convert.cpp
+++ b/icu4c/source/common/convert.cpp
@@ -43,7 +43,7 @@ UnicodeConverterCPP::UnicodeConverterCPP(const UnicodeString& name, UErrorCode&
 {
   char myName[UCNV_MAX_CONVERTER_NAME_LENGTH];
   int i;
-  name.extract(0, i = name.size(), myName);
+  name.extract(0, i = name.length(), myName);
   myName[i]='\0';
   myUnicodeConverter = ucnv_open(myName, &err);
 }
@@ -139,7 +139,7 @@ UnicodeConverterCPP::fromUnicodeString(char*                    target,
   ucnv_reset(&myConverter);
 
 
-  mySourceLength = source.size();
+  mySourceLength = source.length();
   mySource = source.getUChars();
   myTarget = target;
   ucnv_fromUnicode(&myConverter,
@@ -211,7 +211,7 @@ UnicodeConverterCPP::toUnicodeString(UnicodeString&         target,
 		     &err);
 
       /*appends what we got thus far to the UnicodeString*/
-      target.replace((UTextOffset)target.size(),
+      target.replace((UTextOffset)target.length(),
              myTargetUCharsAlias - myTargetUChars,
              myTargetUChars,
              myTargetUCharsAlias - myTargetUChars);
diff --git a/icu4c/source/common/cpputils.cpp b/icu4c/source/common/cpputils.cpp
index 2c5cc4a6f1..6d5374d929 100644
--- a/icu4c/source/common/cpputils.cpp
+++ b/icu4c/source/common/cpputils.cpp
@@ -15,10 +15,10 @@ void T_fillOutputParams(const UnicodeString* temp,
             UErrorCode* status) 
 {
   
-  const int32_t actual = temp->size();
+  const int32_t actual = temp->length();
   const bool_t overflowed = actual >= resultLength;
   const int32_t returnedSize = icu_min(actual, resultLength-1);
-  if ((temp->size() < resultLength) && (result != temp->getUChars()) && (returnedSize > 0)) {
+  if ((temp->length() < resultLength) && (result != temp->getUChars()) && (returnedSize > 0)) {
     u_strcpy(result, temp->getUChars());
   }
   
diff --git a/icu4c/source/common/locid.cpp b/icu4c/source/common/locid.cpp
index 317e721e10..e4074788c9 100644
--- a/icu4c/source/common/locid.cpp
+++ b/icu4c/source/common/locid.cpp
@@ -172,20 +172,20 @@ Locale::Locale( const   UnicodeString&  newLanguage,
   UnicodeString newVariantCopy(newVariant);
   
   
-  if (newCountry.size() > 0 ||
-      newVariantCopy.size() > 0 )
+  if (newCountry.length() > 0 ||
+      newVariantCopy.length() > 0 )
     {
       togo += sep;
       togo += newCountry;
     }
   
-  int vsize = newVariantCopy.size();
+  int vsize = newVariantCopy.length();
     if (vsize > 0)
       {
     int i = 0;
     //We need to trim variant codes : (_*)$var(_*) --> $var 
     while ((i<vsize) && newVariantCopy[i] == sep) newVariantCopy.remove(i++, 1);
-    i = newVariantCopy.size() - 1;
+    i = newVariantCopy.length() - 1;
     while (i && (newVariantCopy[i] == sep)) newVariantCopy.remove(i--, 1);
     
     togo += sep ;
@@ -331,7 +331,7 @@ Locale::setHashCode()
   fullNameUString += UnicodeString(country, "");
   fullNameUString += UnicodeString(variant, "");
   const UChar *key       = fullNameUString.getUChars();
-  int32_t len           = fullNameUString.size();
+  int32_t len           = fullNameUString.length();
   int32_t hash          = 0;
   const UChar *limit     = key + len;
   int32_t inc           = (len >= 128 ? len/64 : 1);
@@ -431,7 +431,7 @@ Locale::getISO3Language(UnicodeString& lang, UErrorCode& status) const
       return lang;
 
     lang = uloc_getISO3Language(fullName);
-    if (lang.size() == 0)
+    if (lang.length() == 0)
       status = U_MISSING_RESOURCE_ERROR;
     
     return lang;
@@ -452,7 +452,7 @@ Locale::getISO3Country(UnicodeString& cntry, UErrorCode& status) const
         return cntry;
 
     cntry = uloc_getISO3Country(fullName);
-    if (cntry.size() == 0)
+    if (cntry.length() == 0)
         status = U_MISSING_RESOURCE_ERROR;
 
     return cntry;
@@ -778,7 +778,7 @@ Locale::getLanguagesForCountry(const UnicodeString& country, int32_t& count)
       break;
       UnicodeString compressedValues;
       compressedCtry2LangMapping.extractBetween(i, j, compressedValues);
-      UnicodeString *values = new UnicodeString[compressedValues.size() / 2];
+      UnicodeString *values = new UnicodeString[compressedValues.length() / 2];
       int32_t valLen = sizeof(values) / sizeof(values[0]);
       for (int32_t k = 0; k < valLen; ++k)
     compressedValues.extractBetween(k * 2, (k * 2) + 2, values[k]);
diff --git a/icu4c/source/common/normlzr.cpp b/icu4c/source/common/normlzr.cpp
index 0404302ba6..085007eee9 100644
--- a/icu4c/source/common/normlzr.cpp
+++ b/icu4c/source/common/normlzr.cpp
@@ -188,14 +188,14 @@ Normalizer::compose(const UnicodeString& source,
   uint16_t minDecomp = compat ? 0 : DecompData::MAX_COMPAT;
   
     UTextOffset i = 0;
-    while (i < source.size() || explodePos != EMPTY) {
+    while (i < source.length() || explodePos != EMPTY) {
         // Get the next char from either the buffer or the source
       UChar ch;
       if (explodePos == EMPTY) {
     ch = source[i++];
       } else {
     ch = explodeBuf[explodePos++];
-    if (explodePos >= explodeBuf.size()) {
+    if (explodePos >= explodeBuf.length()) {
       explodePos = EMPTY;
       explodeBuf.truncate(0);
     }
@@ -209,7 +209,7 @@ Normalizer::compose(const UnicodeString& source,
       if (type == ComposeData::BASE) {
     classesSeen = 0;
     baseIndex = index;
-    basePos = result.size();
+    basePos = result.length();
     result += ch;
       }
       else if (type == ComposeData::COMBINING || type == ComposeData::NON_COMPOSING_COMBINING)
@@ -244,7 +244,7 @@ Normalizer::compose(const UnicodeString& source,
           // base character.  There are only four characters in Unicode that have
           // this problem.  If they are fixed in Unicode 3.0, this code can go away.
           //
-          UTextOffset len = result.size();
+          UTextOffset len = result.length();
           if (len - basePos > 1) {
         for (UTextOffset j = basePos+1; j < len; j++) {
           explodeBuf += result[j];
@@ -273,7 +273,7 @@ Normalizer::compose(const UnicodeString& source,
       else if (type == ComposeData::INITIAL_JAMO) {
     classesSeen = 0;
     baseIndex = ComposeData::INITIAL_JAMO_INDEX;
-    basePos = result.size();
+    basePos = result.length();
     result += ch;
       }
       else if (type == ComposeData::MEDIAL_JAMO && classesSeen == 0
@@ -345,14 +345,14 @@ UChar Normalizer::nextCompose()
         uint16_t index = charInfo >> ComposeData::INDEX_SHIFT;
         
         if (type == ComposeData::BASE) {
-            if (buffer.size() > 0 && chFromText && explodePos == EMPTY) {
+            if (buffer.length() > 0 && chFromText && explodePos == EMPTY) {
                 // When we hit a base char in the source text, we can return the text
                 // that's been composed so far.  We'll re-process this char next time through.
                 break;
             }
             classesSeen = 0;
             baseIndex = index;
-            basePos = buffer.size();
+            basePos = buffer.length();
             buffer += ch;
             lastBase = ch;
         }
@@ -390,7 +390,7 @@ UChar Normalizer::nextCompose()
                 // base character.  There are only four characters in Unicode that have
                 // this problem.  If they are fixed in Unicode 3.0, this code can go away.
                 //
-                UTextOffset len = buffer.size();
+                UTextOffset len = buffer.length();
                 if (len - basePos > 1) {
                     for (UTextOffset j = basePos+1; j < len; j++) {
                         explodeBuf += buffer[j];
@@ -417,14 +417,14 @@ UChar Normalizer::nextCompose()
             explodePos = 0;
         }
         else if (type == ComposeData::INITIAL_JAMO) {
-            if (buffer.size() > 0 && chFromText && explodePos == EMPTY) {
+            if (buffer.length() > 0 && chFromText && explodePos == EMPTY) {
                 // When we hit a base char in the source text, we can return the text
                 // that's been composed so far.  We'll re-process this char next time through.
                 break;
             }
             classesSeen = 0;
             baseIndex = ComposeData::INITIAL_JAMO_INDEX;
-            basePos = buffer.size();
+            basePos = buffer.length();
             buffer += ch;
         }
         else if (type == ComposeData::MEDIAL_JAMO && classesSeen == 0
@@ -461,15 +461,15 @@ UChar Normalizer::nextCompose()
             chFromText = TRUE;
         } else {
             ch = explodeBuf[explodePos++];
-            if (explodePos >= explodeBuf.size()) {
+            if (explodePos >= explodeBuf.length()) {
                 explodePos = EMPTY;
                 explodeBuf.truncate(0);
             }
             chFromText = FALSE;
         }
     }
-    if (buffer.size() > 0) {
-        bufferLimit = buffer.size() - 1;
+    if (buffer.length() > 0) {
+        bufferLimit = buffer.length() - 1;
         ch = buffer[0];
     } else {
         ch = DONE;
@@ -514,7 +514,7 @@ UChar Normalizer::prevCompose()
         }
     }
     // If there's more than one character in the buffer, compose it all at once....
-    if (buffer.size() > 0) {
+    if (buffer.length() > 0) {
         // TODO: The performance of this is awful; add a way to compose
         // a UnicodeString& in place.
       UnicodeString composed;
@@ -522,8 +522,8 @@ UChar Normalizer::prevCompose()
       buffer.truncate(0);
       buffer += composed;
         
-        if (buffer.size() > 1) {
-            bufferLimit = bufferPos = buffer.size() - 1;
+        if (buffer.length() > 1) {
+            bufferLimit = bufferPos = buffer.length() - 1;
             ch = buffer[bufferPos];
         } else {
             ch = buffer[0];
@@ -538,7 +538,7 @@ UChar Normalizer::prevCompose()
 
 void Normalizer::bubbleAppend(UnicodeString& target, UChar ch, uint32_t cclass) {
     UTextOffset i;
-    for (i = target.size() - 1; i > 0; --i) {
+    for (i = target.length() - 1; i > 0; --i) {
         uint32_t iClass = getComposeClass(target[i]);
 
         if (iClass == 1 || iClass <= cclass) {      // 1 means combining class 0
@@ -602,7 +602,7 @@ Normalizer::decompose(const UnicodeString& source,
   
   result.truncate(0);
   
-  for (UTextOffset i = 0; i < source.size(); ++i) {
+  for (UTextOffset i = 0; i < source.length(); ++i) {
     UChar ch = source[i];
     
     uint16_t offset = ucmp16_getu(DecompData::offsets, ch);
@@ -666,14 +666,14 @@ UChar Normalizer::nextDecomp()
       buffer += ch;
         }
       
-      if (buffer.size() > 1 && needToReorder) {
+      if (buffer.length() > 1 && needToReorder) {
     // If there is more than one combining character in the buffer,
     // put them into the canonical order.
     // But we don't need to sort if only characters are the ones that
     // resulted from decomosing the base character.
     fixCanonical(buffer);
       }
-      bufferLimit = buffer.size() - 1;
+      bufferLimit = buffer.length() - 1;
       ch = buffer[0];
     } else {
       // Just use this character, but first advance to the next one
@@ -683,7 +683,7 @@ UChar Normalizer::nextDecomp()
       if (hangul && ch >= HANGUL_BASE && ch < HANGUL_LIMIT) {
     initBuffer();
     hangulToJamo(ch, buffer, minDecomp);
-    bufferLimit = buffer.size() - 1;
+    bufferLimit = buffer.length() - 1;
     ch = buffer[0];
       }
     }
@@ -733,18 +733,18 @@ UChar Normalizer::prevDecomp() {
             text->next();
         }
 
-        if (buffer.size() > 1) {
+        if (buffer.length() > 1) {
             // If there is more than one combining character in the buffer,
             // put them into the canonical order.
             fixCanonical(buffer);
         }
-        bufferLimit = bufferPos = buffer.size() - 1;
+        bufferLimit = bufferPos = buffer.length() - 1;
         ch = buffer[bufferPos];
     }
     else if (hangul && ch >= HANGUL_BASE && ch < HANGUL_LIMIT) {
         initBuffer();
         hangulToJamo(ch, buffer, minDecomp);
-        bufferLimit = bufferPos = buffer.size() - 1;
+        bufferLimit = bufferPos = buffer.length() - 1;
         ch = buffer[bufferPos];
     }
     return ch;
@@ -762,7 +762,7 @@ uint8_t Normalizer::getClass(UChar ch) {
  * @param result the string to fix.
  */
 void Normalizer::fixCanonical(UnicodeString& result) {
-    UTextOffset i = result.size() - 1;
+    UTextOffset i = result.length() - 1;
     uint8_t currentType = getClass(result[i]);
     uint8_t lastType;
     
@@ -781,7 +781,7 @@ void Normalizer::fixCanonical(UnicodeString& result) {
             result[i+1] = temp;
 
             // if not at end, backup (one further, to compensate for for-loop)
-            if (i < result.size() - 2) {
+            if (i < result.length() - 2) {
                 i += 2;
             }
             // reset type, since we swapped.
@@ -1159,7 +1159,7 @@ void Normalizer::jamoAppend(UChar ch, uint16_t decompLimit, UnicodeString& dest)
 
 void Normalizer::jamoToHangul(UnicodeString& buffer, UTextOffset start) {
     UTextOffset out = start;
-    UTextOffset limit = buffer.size() - 1;
+    UTextOffset limit = buffer.length() - 1;
 
     UTextOffset in;
     uint16_t l, v, t;
@@ -1188,7 +1188,7 @@ void Normalizer::jamoToHangul(UnicodeString& buffer, UTextOffset start) {
             buffer[out++] = ch;
         }
     }
-    while (in < buffer.size()) {
+    while (in < buffer.length()) {
         buffer[out++] = buffer[in++];
     }
 
diff --git a/icu4c/source/common/resbund.cpp b/icu4c/source/common/resbund.cpp
index 39faeb2429..1c7df466cf 100644
--- a/icu4c/source/common/resbund.cpp
+++ b/icu4c/source/common/resbund.cpp
@@ -225,7 +225,7 @@ ResourceBundle::LocaleFallbackIterator::nextLocale(UErrorCode& status)
   if(status != U_USING_DEFAULT_ERROR) 
     status = U_USING_FALLBACK_ERROR;
   
-  if(fLocale.size() == 0) {
+  if(fLocale.length() == 0) {
     if(fUseDefaultLocale && !fTriedDefaultLocale) {
       fLocale = fDefaultLocale;
       fTriedDefaultLocale = TRUE;
@@ -249,7 +249,7 @@ ResourceBundle::LocaleFallbackIterator::nextLocale(UErrorCode& status)
 void
 ResourceBundle::LocaleFallbackIterator::chopLocale()
 {
-  int32_t size = fLocale.size();
+  int32_t size = fLocale.length();
   int32_t i;
   
   for(i = size - 1; i > 0; i--) 
@@ -381,7 +381,7 @@ ResourceBundle::constructForLocale(const PathInfo& path,
   // fRealLocale can be inited in three ways, see 1), 2), 3)
   UnicodeString returnedLocale;
   locale.getName(returnedLocale);
-  if (returnedLocale.size()!=0) {
+  if (returnedLocale.length()!=0) {
 	// 1) Desired Locale has a name
 	fRealLocale = Locale(returnedLocale); 
   } else {
@@ -922,8 +922,8 @@ ResourceBundle::getVersionNumber()  const
     // the end).
     int32_t len = icu_strlen(ICU_VERSION);
     int32_t minor_len = 0;
-    if(U_SUCCESS(status) && minor_version.size() > 0) 
-      minor_len = minor_version.size();
+    if(U_SUCCESS(status) && minor_version.length() > 0) 
+      minor_len = minor_version.length();
     len += (minor_len > 0) ? minor_len : 1 /*==icu_strlen(kDefaultMinorVersion)*/;
     ++len; // Add length of separator
     
@@ -1289,7 +1289,7 @@ ResourceBundle::PathInfo::openFile(const UnicodeString& localeName) const
 {
   if(fWPrefix) {
     //use the wide version of fopen in TPlatformUtilities.
-    int32_t nameSize = localeName.size();
+    int32_t nameSize = localeName.length();
     char* temp = new char[nameSize + 1];
     localeName.extract(0, nameSize, temp);
     temp[nameSize] = 0;
@@ -1328,7 +1328,7 @@ ResourceBundle::PathInfo::openFile(const UnicodeString& localeName) const
   else {
     //open file using standard char* routines
     UnicodeString workingName(makeCacheKey(localeName));
-    int32_t size = workingName.size();
+    int32_t size = workingName.length();
     char* returnVal = new char[size + 1];
     workingName.extract(0, size, returnVal, "");
     returnVal[size] = 0;
diff --git a/icu4c/source/common/unistr.cpp b/icu4c/source/common/unistr.cpp
index 669dd83209..bb9b44369f 100644
--- a/icu4c/source/common/unistr.cpp
+++ b/icu4c/source/common/unistr.cpp
@@ -1296,7 +1296,7 @@ T_UnicodeString_getUChars(const UnicodeString *s)
 U_CFUNC int32_t
 T_UnicodeString_extract(const UnicodeString *s, char *dst)
 {
-  return s->extract(0,s->size(),dst,"");
+  return s->extract(0, s->length(), dst, "");
 }
 
 
diff --git a/icu4c/source/i18n/calendar.cpp b/icu4c/source/i18n/calendar.cpp
index d6d238a563..9d1a35b02f 100644
--- a/icu4c/source/i18n/calendar.cpp
+++ b/icu4c/source/i18n/calendar.cpp
@@ -671,7 +671,7 @@ int32_t Calendar::stringToDayNumber(const UnicodeString& string, UErrorCode& sta
     // ResourceBundle returns all data in string form, so we have to convert it here.)
     if (U_FAILURE(status)) return 0;
 
-    int32_t len = string.size();
+    int32_t len = string.length();
     char *number = new char[1 + len];
     if (number == 0) { status = U_MEMORY_ALLOCATION_ERROR; return 0; }
     char *end;
diff --git a/icu4c/source/i18n/choicfmt.cpp b/icu4c/source/i18n/choicfmt.cpp
index 875f9e12dd..220cd6c5eb 100644
--- a/icu4c/source/i18n/choicfmt.cpp
+++ b/icu4c/source/i18n/choicfmt.cpp
@@ -240,11 +240,11 @@ ChoiceFormat::applyPattern(const UnicodeString& newPattern,
     double startValue = 0;
     double oldStartValue = icu_getNaN();
     bool_t inQuote = FALSE;
-    for(int i = 0; i < newPattern.size(); ++i) {
+    for(int i = 0; i < newPattern.length(); ++i) {
         UChar ch = newPattern[i];
         if(ch == 0x0027 /*'\''*/) {
             // Check for "''" indicating a literal quote
-            if((i+1) < newPattern.size() && newPattern[i+1] == ch) {
+            if((i+1) < newPattern.length() && newPattern[i+1] == ch) {
                 segments[part] += ch;
                 ++i;
             }
@@ -367,7 +367,7 @@ ChoiceFormat::toPattern(UnicodeString& result) const
         if (text.indexOf(0x0027 /*'\''*/) < 0) 
             result += text;
         else {
-            for (int j = 0; j < text.size(); ++j) {
+            for (int j = 0; j < text.length(); ++j) {
                 UChar c = text[j];
                 result += c;
                 if (c == 0x0027 /*'\''*/) 
@@ -532,13 +532,13 @@ ChoiceFormat::parse(const UnicodeString& text,
     double tempNumber = 0.0;
     for (int i = 0; i < fCount; ++i) {
         UnicodeString tempString = fChoiceFormats[i];
-        if(text.compareBetween(start, tempString.size(), tempString, 0, tempString.size()) == 0) {
-            status.setIndex(start + tempString.size());
+        if(text.compareBetween(start, tempString.length(), tempString, 0, tempString.length()) == 0) {
+            status.setIndex(start + tempString.length());
             tempNumber = fChoiceLimits[i];
             if (status.getIndex() > furthest) {
                 furthest = status.getIndex();
                 bestNumber = tempNumber;
-                if (furthest == text.size()) 
+                if (furthest == text.length()) 
                     break;
             }
         }
diff --git a/icu4c/source/i18n/coleitr.cpp b/icu4c/source/i18n/coleitr.cpp
index ac191082e9..6665574806 100644
--- a/icu4c/source/i18n/coleitr.cpp
+++ b/icu4c/source/i18n/coleitr.cpp
@@ -69,7 +69,7 @@ CollationElementIterator::CollationElementIterator( const UnicodeString& sourceT
         return;
     }
 
-    if ( sourceText.size() != 0 ) {
+    if ( sourceText.length() != 0 ) {
         //
         // A CollationElementIterator is really a two-layered beast.
         // Internally it uses a Normalizer to munge the source text
diff --git a/icu4c/source/i18n/dcfmtsym.cpp b/icu4c/source/i18n/dcfmtsym.cpp
index d987f180a6..99e82142db 100644
--- a/icu4c/source/i18n/dcfmtsym.cpp
+++ b/icu4c/source/i18n/dcfmtsym.cpp
@@ -228,7 +228,7 @@ DecimalFormatSymbols::initialize(const UnicodeString* numberElements, const Unic
     // if the resource data specified the empty string as the monetary decimal
     // separator, that means we should just use the regular separator as the
     // monetary separator
-    if(currencyElements[2].size() == 0)
+    if(currencyElements[2].length() == 0)
         fMonetarySeparator = fDecimalSeparator;
     else
         fMonetarySeparator = currencyElements[2][(UTextOffset)0];
diff --git a/icu4c/source/i18n/decimfmt.cpp b/icu4c/source/i18n/decimfmt.cpp
index 1a3866e516..408f980547 100644
--- a/icu4c/source/i18n/decimfmt.cpp
+++ b/icu4c/source/i18n/decimfmt.cpp
@@ -522,13 +522,13 @@ DecimalFormat::format(  double number,
     if (icu_isNaN(number))
     {
         if (fieldPosition.getField() == NumberFormat::kIntegerField)
-            fieldPosition.setBeginIndex(result.size());
+            fieldPosition.setBeginIndex(result.length());
 
         UnicodeString nan;
         result += fSymbols->getNaN(nan);
 
         if (fieldPosition.getField() == NumberFormat::kIntegerField)
-            fieldPosition.setEndIndex(result.size());
+            fieldPosition.setEndIndex(result.length());
 
         addPadding(result, FALSE, FALSE /*ignored*/);
         return result;
@@ -566,13 +566,13 @@ DecimalFormat::format(  double number,
         result += (isNegative ? fNegativePrefix : fPositivePrefix);
 
         if (fieldPosition.getField() == NumberFormat::kIntegerField)
-            fieldPosition.setBeginIndex(result.size());
+            fieldPosition.setBeginIndex(result.length());
 
         UnicodeString inf;
         result += fSymbols->getInfinity(inf);
 
         if (fieldPosition.getField() == NumberFormat::kIntegerField)
-            fieldPosition.setEndIndex(result.size());
+            fieldPosition.setEndIndex(result.length());
 
         result += (isNegative ? fNegativeSuffix : fPositiveSuffix);
 
@@ -678,7 +678,7 @@ DecimalFormat::subformat(UnicodeString& result,
         // Record field information for caller.
         if (fieldPosition.getField() == NumberFormat::kIntegerField)
         {
-            fieldPosition.setBeginIndex(result.size());
+            fieldPosition.setBeginIndex(result.length());
             fieldPosition.setEndIndex(-1);
         }
         else if (fieldPosition.getField() == NumberFormat::kFractionField)
@@ -731,13 +731,13 @@ DecimalFormat::subformat(UnicodeString& result,
             {
                 // Record field information for caller.
                 if (fieldPosition.getField() == NumberFormat::kIntegerField)
-                    fieldPosition.setEndIndex(result.size());
+                    fieldPosition.setEndIndex(result.length());
 
                 result += (decimal);
 
                 // Record field information for caller.
                 if (fieldPosition.getField() == NumberFormat::kFractionField)
-                    fieldPosition.setBeginIndex(result.size());
+                    fieldPosition.setBeginIndex(result.length());
             }
             // Restores the digit character or pads the buffer with zeros.
             UChar c = ((i < fDigitList->fCount) ?
@@ -750,13 +750,13 @@ DecimalFormat::subformat(UnicodeString& result,
         if (fieldPosition.getField() == NumberFormat::kIntegerField)
         {
             if (fieldPosition.getEndIndex() < 0)
-                fieldPosition.setEndIndex(result.size());
+                fieldPosition.setEndIndex(result.length());
         }
         else if (fieldPosition.getField() == NumberFormat::kFractionField)
         {
             if (fieldPosition.getBeginIndex() < 0)
-                fieldPosition.setBeginIndex(result.size());
-            fieldPosition.setEndIndex(result.size());
+                fieldPosition.setBeginIndex(result.length());
+            fieldPosition.setEndIndex(result.length());
         }
 
         // The exponent is output using the pattern-specified minimum
@@ -793,7 +793,7 @@ DecimalFormat::subformat(UnicodeString& result,
     {
         // Record field information for caller.
         if (fieldPosition.getField() == NumberFormat::kIntegerField)
-            fieldPosition.setBeginIndex(result.size());
+            fieldPosition.setBeginIndex(result.length());
 
         // Output the integer portion.  Here 'count' is the total
         // number of integer digits we will display, including both
@@ -815,7 +815,7 @@ DecimalFormat::subformat(UnicodeString& result,
             digitIndex = fDigitList->fDecimalAt - count;
         }
 
-        int32_t sizeBeforeIntegerPart = result.size();
+        int32_t sizeBeforeIntegerPart = result.length();
 
         int32_t i;
         for (i=count-1; i>=0; --i)
@@ -842,7 +842,7 @@ DecimalFormat::subformat(UnicodeString& result,
 
         // Record field information for caller.
         if (fieldPosition.getField() == NumberFormat::kIntegerField)
-            fieldPosition.setEndIndex(result.size());
+            fieldPosition.setEndIndex(result.length());
 
         // Determine whether or not there are any printable fractional
         // digits.  If we've used up the digits we know there aren't.
@@ -852,7 +852,7 @@ DecimalFormat::subformat(UnicodeString& result,
         // If there is no fraction present, and we haven't printed any
         // integer digits, then print a zero.  Otherwise we won't print
         // _any_ digits, and we won't be able to parse this string.
-        if (!fractionPresent && result.size() == sizeBeforeIntegerPart)
+        if (!fractionPresent && result.length() == sizeBeforeIntegerPart)
             result += (zero);
 
         // Output the decimal separator if we always do so.
@@ -861,7 +861,7 @@ DecimalFormat::subformat(UnicodeString& result,
 
         // Record field information for caller.
         if (fieldPosition.getField() == NumberFormat::kFractionField)
-            fieldPosition.setBeginIndex(result.size());
+            fieldPosition.setBeginIndex(result.length());
 
         for (i=0; i < getMaximumFractionDigits(); ++i)
         {
@@ -897,7 +897,7 @@ DecimalFormat::subformat(UnicodeString& result,
 
         // Record field information for caller.
         if (fieldPosition.getField() == NumberFormat::kFractionField)
-            fieldPosition.setEndIndex(result.size());
+            fieldPosition.setEndIndex(result.length());
     }
 
     result += (isNegative ? fNegativeSuffix : fPositiveSuffix);
@@ -919,7 +919,7 @@ DecimalFormat::subformat(UnicodeString& result,
 void DecimalFormat::addPadding(UnicodeString& result, bool_t hasAffixes,
                                bool_t isNegative) const {
     if (fFormatWidth > 0) {
-        int32_t len = fFormatWidth - result.size();
+        int32_t len = fFormatWidth - result.length();
         if (len > 0) {
             UChar* padding = (UChar*) icu_malloc(sizeof(UChar) * len);
             for (int32_t i=0; i<len; ++i) {
@@ -928,8 +928,8 @@ void DecimalFormat::addPadding(UnicodeString& result, bool_t hasAffixes,
             switch (fPadPosition) {
             case kPadAfterPrefix:
                 if (hasAffixes) {
-                    result.insert(isNegative ? fNegativePrefix.size()
-                                             : fPositivePrefix.size(),
+                    result.insert(isNegative ? fNegativePrefix.length()
+                                             : fPositivePrefix.length(),
                                   padding, len);
                     break;
                 } // else fall through to next case
@@ -938,9 +938,9 @@ void DecimalFormat::addPadding(UnicodeString& result, bool_t hasAffixes,
                 break;
             case kPadBeforeSuffix:
                 if (hasAffixes) {
-                    result.insert(result.size() -
-                                  (isNegative ? fNegativeSuffix.size()
-                                              : fPositiveSuffix.size()),
+                    result.insert(result.length() -
+                                  (isNegative ? fNegativeSuffix.length()
+                                              : fPositiveSuffix.length()),
                                   padding, len);
                     break;
                 } // else fall through to next case
@@ -976,7 +976,7 @@ DecimalFormat::parse(const UnicodeString& text,
     int32_t backup = parsePosition.getIndex();
     int32_t i = backup;
     if (fFormatWidth > 0) {
-        while (i < text.size() && text[(UTextOffset) i] == fPad) {
+        while (i < text.length() && text[(UTextOffset) i] == fPad) {
             ++i;
         }
         parsePosition.setIndex(i);
@@ -986,9 +986,9 @@ DecimalFormat::parse(const UnicodeString& text,
     UnicodeString nan;
     fSymbols->getNaN(nan);
     // If the text is composed of the representation of NaN, returns NaN.
-    if (text.compare(parsePosition.getIndex(), nan.size(), nan,
-                     0, nan.size()) == 0) {
-        parsePosition.setIndex(parsePosition.getIndex() + nan.size());
+    if (text.compare(parsePosition.getIndex(), nan.length(), nan,
+                     0, nan.length()) == 0) {
+        parsePosition.setIndex(parsePosition.getIndex() + nan.length());
         result.setDouble(icu_getNaN());
         return;
     }
@@ -1002,7 +1002,7 @@ DecimalFormat::parse(const UnicodeString& text,
         return;
     } else if (fFormatWidth < 0) {
         i = parsePosition.getIndex();
-        while (i < text.size() && text[(UTextOffset) i] == fPad) {
+        while (i < text.length() && text[(UTextOffset) i] == fPad) {
             ++i;
         }
         parsePosition.setIndex(i);
@@ -1063,23 +1063,23 @@ bool_t DecimalFormat::subparse(const UnicodeString& text, ParsePosition& parsePo
     int32_t backup;
 
     // check for positivePrefix; take longest
-    bool_t gotPositive = text.compare(position,fPositivePrefix.size(),fPositivePrefix,0,
-                                      fPositivePrefix.size()) == 0;
-    bool_t gotNegative = text.compare(position,fNegativePrefix.size(),fNegativePrefix,0,
-                                      fNegativePrefix.size()) == 0;
+    bool_t gotPositive = text.compare(position,fPositivePrefix.length(),fPositivePrefix,0,
+                                      fPositivePrefix.length()) == 0;
+    bool_t gotNegative = text.compare(position,fNegativePrefix.length(),fNegativePrefix,0,
+                                      fNegativePrefix.length()) == 0;
     // If the number is positive and negative at the same time,
     // 1. the number is positive if the positive prefix is longer
     // 2. the number is negative if the negative prefix is longer
     if (gotPositive && gotNegative) {
-        if (fPositivePrefix.size() > fNegativePrefix.size())
+        if (fPositivePrefix.length() > fNegativePrefix.length())
             gotNegative = FALSE;
-        else if (fPositivePrefix.size() < fNegativePrefix.size())
+        else if (fPositivePrefix.length() < fNegativePrefix.length())
             gotPositive = FALSE;
     }
     if(gotPositive)
-        position += fPositivePrefix.size();
+        position += fPositivePrefix.length();
     else if(gotNegative)
-        position += fNegativePrefix.size();
+        position += fNegativePrefix.length();
     else {
         parsePosition.setErrorIndex(position);
         return FALSE;
@@ -1088,11 +1088,11 @@ bool_t DecimalFormat::subparse(const UnicodeString& text, ParsePosition& parsePo
     status[fgStatusInfinite] = FALSE;
     UnicodeString inf;
     fSymbols->getInfinity(inf);
-    if (!isExponent && text.compare(position,inf.size(),inf,0,
-                                    inf.size()) == 0)
+    if (!isExponent && text.compare(position,inf.length(),inf,0,
+                                    inf.length()) == 0)
     {
         // Found a infinite number.
-        position += inf.size();
+        position += inf.length();
         status[fgStatusInfinite] = TRUE;
     } else {
         // We now have a string of digits, possibly with grouping symbols,
@@ -1120,7 +1120,7 @@ bool_t DecimalFormat::subparse(const UnicodeString& text, ParsePosition& parsePo
         int32_t digitCount = 0;
 
         backup = -1;
-        for (; position < text.size(); ++position)
+        for (; position < text.length(); ++position)
         {
             UChar ch = text[(UTextOffset)position];
 
@@ -1192,7 +1192,7 @@ bool_t DecimalFormat::subparse(const UnicodeString& text, ParsePosition& parsePo
                 // Parse sign, if present
                 bool_t negExp = FALSE;
                 int32_t pos = position + 1; // position + exponentSep.length();
-                if (pos < text.size()) {
+                if (pos < text.length()) {
                     ch = text[(UTextOffset) pos];
                     if (ch == fSymbols->getPlusSign()) {
                         ++pos;
@@ -1204,7 +1204,7 @@ bool_t DecimalFormat::subparse(const UnicodeString& text, ParsePosition& parsePo
 
                 DigitList exponentDigits;
                 exponentDigits.fCount = 0;
-                while (pos < text.size()) {
+                while (pos < text.length()) {
                     digit = text[(UTextOffset) pos] - zero;
                     //~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~~*~
                     // TEMPORARY WORKAROUND
@@ -1264,17 +1264,17 @@ bool_t DecimalFormat::subparse(const UnicodeString& text, ParsePosition& parsePo
 
     // check for positiveSuffix
     if (gotPositive)
-        gotPositive = text.compare(position,fPositiveSuffix.size(),fPositiveSuffix,0,
-                                   fPositiveSuffix.size()) == 0;
+        gotPositive = text.compare(position,fPositiveSuffix.length(),fPositiveSuffix,0,
+                                   fPositiveSuffix.length()) == 0;
     if (gotNegative)
-        gotNegative = text.compare(position,fNegativeSuffix.size(),fNegativeSuffix,0,
-                                   fNegativeSuffix.size()) == 0;
+        gotNegative = text.compare(position,fNegativeSuffix.length(),fNegativeSuffix,0,
+                                   fNegativeSuffix.length()) == 0;
 
     // if both match, take longest
     if (gotPositive && gotNegative) {
-        if (fPositiveSuffix.size() > fNegativeSuffix.size())
+        if (fPositiveSuffix.length() > fNegativeSuffix.length())
             gotNegative = FALSE;
-        else if (fPositiveSuffix.size() < fNegativeSuffix.size())
+        else if (fPositiveSuffix.length() < fNegativeSuffix.length())
             gotPositive = FALSE;
     }
 
@@ -1285,8 +1285,8 @@ bool_t DecimalFormat::subparse(const UnicodeString& text, ParsePosition& parsePo
     }
 
     parsePosition.setIndex(position +
-                           (gotPositive ? fPositiveSuffix.size() :
-                            fNegativeSuffix.size())); // mark success!
+                           (gotPositive ? fPositiveSuffix.length() :
+                            fNegativeSuffix.length())); // mark success!
 
     status[fgStatusPositive] = gotPositive;
 
@@ -1781,7 +1781,7 @@ void DecimalFormat::expandAffixes() {
 void DecimalFormat::expandAffix(const UnicodeString& pattern,
                                 UnicodeString& affix) const {
     affix.remove();
-    for (int i=0; i<pattern.size(); ) {
+    for (int i=0; i<pattern.length(); ) {
         UChar c = pattern.charAt(i++);
         if (c == kQuote) {
             c = pattern.charAt(i++);
@@ -1789,7 +1789,7 @@ void DecimalFormat::expandAffix(const UnicodeString& pattern,
             case kCurrencySign:
                 {
                     UnicodeString s;
-                    if (i<pattern.size() &&
+                    if (i<pattern.length() &&
                         pattern.charAt(i) == kCurrencySign) {
                         ++i;
                         affix += fSymbols->getInternationalCurrencySymbol(s);
@@ -1839,11 +1839,11 @@ void DecimalFormat::appendAffix(UnicodeString& buffer,
         appendAffix(buffer, expAffix, localized);
     } else {
         int i;
-        for (int pos=0; pos<affixPattern->size(); pos=i) {
+        for (int pos=0; pos<affixPattern->length(); pos=i) {
             i = affixPattern->indexOf(kQuote, pos);
             if (i < 0) {
                 UnicodeString s;
-                affixPattern->extractBetween(pos, affixPattern->size(), s);
+                affixPattern->extractBetween(pos, affixPattern->length(), s);
                 appendAffix(buffer, s, localized);
                 break;
             }
@@ -1858,7 +1858,7 @@ void DecimalFormat::appendAffix(UnicodeString& buffer,
                 buffer.append(c);
                 // Fall through and append another kQuote below
             } else if (c == kCurrencySign &&
-                       i<affixPattern->size() &&
+                       i<affixPattern->length() &&
                        affixPattern->charAt(i) == kCurrencySign) {
                 ++i;
                 buffer.append(c);
@@ -1924,7 +1924,7 @@ DecimalFormat::appendAffix(    UnicodeString& buffer,
     if (affix.indexOf(0x0027 /*'\''*/) < 0)
         buffer += affix;
     else {
-        for (int32_t j = 0; j < affix.size(); ++j) {
+        for (int32_t j = 0; j < affix.length(); ++j) {
             UChar c = affix[j];
             buffer += c;
             if (c == 0x0027 /*'\''*/) buffer += c;
@@ -2171,7 +2171,7 @@ DecimalFormat::applyPattern(const UnicodeString& pattern,
         int32_t start = pos;
         bool_t isPartDone = FALSE;
 
-        for (; !isPartDone && pos < pattern.size(); ++pos) {
+        for (; !isPartDone && pos < pattern.length(); ++pos) {
             UChar ch = pattern[(UTextOffset) pos];
             switch (subpart) {
             case 0: // Pattern proper subpart (between prefix & suffix)
@@ -2244,7 +2244,7 @@ DecimalFormat::applyPattern(const UnicodeString& pattern,
                             return;
                         }
                         // Check for positive prefix
-                        if ((pos+1) < pattern.size()
+                        if ((pos+1) < pattern.length()
                             && pattern[(UTextOffset) (pos+1)] == plus) {
                             expSignAlways = TRUE;
                             ++pos;
@@ -2252,7 +2252,7 @@ DecimalFormat::applyPattern(const UnicodeString& pattern,
                         // Use lookahead to parse out the exponential part of the
                         // pattern, then jump into suffix subpart.
                         expDigits = 0;
-                        while (++pos < pattern.size() &&
+                        while (++pos < pattern.length() &&
                                pattern[(UTextOffset) pos] == zeroDigit) {
                             ++expDigits;
                         }
@@ -2292,7 +2292,7 @@ DecimalFormat::applyPattern(const UnicodeString& pattern,
                 } else if (ch == kCurrencySign) {
                     // Use lookahead to determine if the currency sign is
                     // doubled or not.
-                    bool_t doubled = (pos + 1) < pattern.size() &&
+                    bool_t doubled = (pos + 1) < pattern.length() &&
                         pattern[(UTextOffset) (pos+1)] == kCurrencySign;
                     affix->append(kQuote); // Encode currency
                     if (doubled) {
@@ -2305,7 +2305,7 @@ DecimalFormat::applyPattern(const UnicodeString& pattern,
                     // A quote outside quotes indicates either the opening
                     // quote or two quotes, which is a quote literal.  That is,
                     // we have the first quote in 'do' or o''clock.
-                    if ((pos+1) < pattern.size() &&
+                    if ((pos+1) < pattern.length() &&
                         pattern[(UTextOffset) (pos+1)] == kQuote) {
                         ++pos;
                         affix->append(kQuote); // Encode quote
@@ -2345,7 +2345,7 @@ DecimalFormat::applyPattern(const UnicodeString& pattern,
                     // Fall through to append(ch)
                 } else if (ch == padEscape) {
                     if (padPos >= 0 ||               // Multiple pad specifiers
-                        (pos+1) == pattern.size()) { // Nothing after padEscape
+                        (pos+1) == pattern.length()) { // Nothing after padEscape
                         debug("Multiple pad specifiers")
                         status = U_ILLEGAL_ARGUMENT_ERROR;
                         return;
@@ -2373,7 +2373,7 @@ DecimalFormat::applyPattern(const UnicodeString& pattern,
                 // quote or two quotes, which is a quote literal.  That is,
                 // we have the second quote in 'do' or 'don''t'.
                 if (ch == kQuote) {
-                    if ((pos+1) < pattern.size() &&
+                    if ((pos+1) < pattern.length() &&
                         pattern[(UTextOffset) (pos+1)] == kQuote) {
                         ++pos;
                         affix->append(kQuote); // Encode quote
@@ -2389,11 +2389,11 @@ DecimalFormat::applyPattern(const UnicodeString& pattern,
         }
 
         if (sub0Limit == 0) {
-            sub0Limit = pattern.size();
+            sub0Limit = pattern.length();
         }
 
         if (sub2Limit == 0) {
-            sub2Limit = pattern.size();
+            sub2Limit = pattern.length();
         }
 
         /* Handle patterns with no '0' pattern character.  These patterns
@@ -2513,7 +2513,7 @@ DecimalFormat::applyPattern(const UnicodeString& pattern,
         }
     }
 
-    if (pattern.size() == 0) {
+    if (pattern.length() == 0) {
         delete fNegPrefixPattern;
         delete fNegSuffixPattern;
         fNegPrefixPattern = NULL;
diff --git a/icu4c/source/i18n/mergecol.cpp b/icu4c/source/i18n/mergecol.cpp
index 1909b197db..e4adeb8e88 100644
--- a/icu4c/source/i18n/mergecol.cpp
+++ b/icu4c/source/i18n/mergecol.cpp
@@ -160,7 +160,7 @@ MergeCollation::getPattern(UnicodeString& result, bool_t withWhiteSpace) const
     {
       // if the entry is an expanding ligature, queue up the entries until
       // the last same ligature has been processed.
-      if (entry->extension.size() != 0)
+      if (entry->extension.length() != 0)
         {
           if (extList == NULL)
         {
@@ -268,7 +268,7 @@ void MergeCollation::addPattern(const   UnicodeString&  pattern,
                                 Normalizer::EMode decompMode,
                 UErrorCode&      success)
 {
-  if (U_FAILURE(success) || (pattern.size() == 0))
+  if (U_FAILURE(success) || (pattern.length() == 0))
     {
       return;
     }
@@ -319,7 +319,7 @@ const PatternEntry* MergeCollation::getItemAt(UTextOffset index) const {
 const PatternEntry* MergeCollation::findLastWithNoExtension(int32_t i) const {
   for (--i;i >= 0; --i) {
     PatternEntry* entry = patterns->at(i);
-    if ((entry != 0) && (entry->extension.size() == 0)) {
+    if ((entry != 0) && (entry->extension.length() == 0)) {
       return entry;
     }
   }
@@ -350,7 +350,7 @@ void MergeCollation::fixEntry(PatternEntry* newEntry,
       // replace the previous one.  This will improve the single
       // char entries dramatically which is the majority of the 
       // entries.
-      if (newEntry->chars.size() == 1)
+      if (newEntry->chars.length() == 1)
     {
       UChar c = newEntry->chars[0];
       int32_t statusIndex = c >> BYTEPOWER;
@@ -401,7 +401,7 @@ void MergeCollation::fixEntry(PatternEntry* newEntry,
     }
 
       // Do not change the last entry if the new entry is a expanding character
-      if (excess.size() != 0)
+      if (excess.length() != 0)
     {
       // newEntry.extension = excess + newEntry.extensions;
       newEntry->extension.insert(0, excess);
@@ -451,7 +451,7 @@ MergeCollation::findLastEntry(const PatternEntry*   lastEntry,
 
       // If the last entry is a single char entry and has been installed, 
       // that means the last index is the real last index.
-      if (lastEntry->chars.size() == 1)
+      if (lastEntry->chars.length() == 1)
     {
       int32_t index = lastEntry->chars[0] >> BYTEPOWER;
 
@@ -497,11 +497,11 @@ MergeCollation::findLastEntry(const PatternEntry*   lastEntry,
           // be 'Q'.  We save the characters that didn't match ("uestion-mark" in
           // this case), and then return the next index.
           //
-          if (entry->chars.compareBetween(0, entry->chars.size(),
-                          lastEntry->chars,0,entry->chars.size()) == 0)
+          if (entry->chars.compareBetween(0, entry->chars.length(),
+                          lastEntry->chars,0,entry->chars.length()) == 0)
         {
-          lastEntry->chars.extractBetween(entry->chars.size(), 
-                          lastEntry->chars.size(),
+          lastEntry->chars.extractBetween(entry->chars.length(), 
+                          lastEntry->chars.length(),
                           buffer);
           excess += buffer;
           break;
diff --git a/icu4c/source/i18n/msgfmt.cpp b/icu4c/source/i18n/msgfmt.cpp
index b72b90a843..47cfb492a7 100644
--- a/icu4c/source/i18n/msgfmt.cpp
+++ b/icu4c/source/i18n/msgfmt.cpp
@@ -220,11 +220,11 @@ MessageFormat::applyPattern(const UnicodeString& newPattern,
     bool_t inQuote = FALSE;
     int32_t braceStack = 0;
     fMaxOffset = -1;
-    for (int i = 0; i < newPattern.size(); ++i) {
+    for (int i = 0; i < newPattern.length(); ++i) {
         UChar ch = newPattern[i];
         if (part == 0) {
             if (ch == 0x0027 /*'\''*/) {
-                if (i + 1 < newPattern.size()
+                if (i + 1 < newPattern.length()
                     && newPattern[i+1] == 0x0027 /*'\''*/) {
                     segments[part] += ch;  // handle doubles
                     ++i;
@@ -402,7 +402,7 @@ MessageFormat::toPattern(UnicodeString& result) const
     }
     result += 0x007D /*'}'*/;
   }
-  copyAndFixQuotes(fPattern, lastOffset, fPattern.size(), result);
+  copyAndFixQuotes(fPattern, lastOffset, fPattern.length(), result);
   return result;
 }
  
@@ -661,7 +661,7 @@ MessageFormat::format(const Formattable* arguments,
     }
     buffer.remove();
     // Appends the rest of the pattern characters after the real last offset.
-    fPattern.extract(lastOffset, fPattern.size(), buffer);
+    fPattern.extract(lastOffset, fPattern.length(), buffer);
     result += buffer;
     return result;
 }
@@ -724,11 +724,11 @@ MessageFormat::parse(const UnicodeString& source,
       // if at end, use longest possible match
       // otherwise uses first match to intervening string
       // does NOT recursively try all possibilities
-      int32_t tempLength = (i != fMaxOffset) ? fOffsets[i+1] : fPattern.size();
+      int32_t tempLength = (i != fMaxOffset) ? fOffsets[i+1] : fPattern.length();
 
       int32_t next;
       if (patternOffset >= tempLength) {
-    next = source.size();
+        next = source.length();
       }
       else {
     UnicodeString buffer;
@@ -777,7 +777,7 @@ MessageFormat::parse(const UnicodeString& source,
       sourceOffset = tempStatus.getIndex(); // update
     }
   }
-  int32_t len = fPattern.size() - patternOffset;
+  int32_t len = fPattern.length() - patternOffset;
   if (len == 0 || 
       fPattern.compare(patternOffset, len, source, sourceOffset, len) == 0) {
     status.setIndex(sourceOffset + len);
@@ -948,7 +948,7 @@ MessageFormat::makeFormat(int32_t position,
         return;
     }
     fMaxOffset = offsetNumber;
-    fOffsets[offsetNumber] = segments[0].size();
+    fOffsets[offsetNumber] = segments[0].length();
     fArgumentNumbers[offsetNumber] = argumentNumber;
 
     // now get the format
diff --git a/icu4c/source/i18n/ptnentry.cpp b/icu4c/source/i18n/ptnentry.cpp
index 45afb9977a..b39a5e9fd7 100644
--- a/icu4c/source/i18n/ptnentry.cpp
+++ b/icu4c/source/i18n/ptnentry.cpp
@@ -140,7 +140,7 @@ void PatternEntry::addToBuffer(UnicodeString& toAddTo,
                    bool_t showWhiteSpace,
                    const PatternEntry* lastEntry) const
 {
-  if (showWhiteSpace && toAddTo.size() > 0)
+  if (showWhiteSpace && toAddTo.length() > 0)
     // Adds new line before each primary strength entry.
     if (strength == Collator::PRIMARY || lastEntry != NULL)
       toAddTo += 0x000A/*'\n'*/;
@@ -169,7 +169,7 @@ void PatternEntry::addToBuffer(UnicodeString& toAddTo,
   appendQuoted(chars,toAddTo);
   // If there's an expending char and needs to be shown, 
   // append that after the entry
-  if (showExtension && extension.size() != 0) {
+  if (showExtension && extension.length() != 0) {
     toAddTo += 0x002F/*'/'*/;
     appendQuoted(extension,toAddTo);
   }
@@ -249,7 +249,7 @@ PatternEntry *PatternEntry::Parser::next(UErrorCode &status)
   newChars.remove();
   newExtensions.remove();
 
-  while (index < pattern.size())
+  while (index < pattern.length())
     {
       UChar ch = pattern[index];
 
@@ -261,7 +261,7 @@ PatternEntry *PatternEntry::Parser::next(UErrorCode &status)
         }
       else
         {
-          if ((newChars.size() == 0) || inChars)
+          if ((newChars.length() == 0) || inChars)
         {
           newChars += ch;
         }
@@ -338,7 +338,7 @@ PatternEntry *PatternEntry::Parser::next(UErrorCode &status)
           inQuote = TRUE;
           ch = pattern[++index];
 
-          if (newChars.size() == 0)
+          if (newChars.length() == 0)
         {
           newChars += ch;
         }
@@ -394,7 +394,7 @@ PatternEntry *PatternEntry::Parser::next(UErrorCode &status)
       return NULL;
     }
 
-  if (newChars.size() == 0)
+  if (newChars.length() == 0)
     {
       status = U_INVALID_FORMAT_ERROR;
       return NULL;
diff --git a/icu4c/source/i18n/smpdtfmt.cpp b/icu4c/source/i18n/smpdtfmt.cpp
index 2faeb2e775..5b74d5db9b 100644
--- a/icu4c/source/i18n/smpdtfmt.cpp
+++ b/icu4c/source/i18n/smpdtfmt.cpp
@@ -404,19 +404,19 @@ SimpleDateFormat::format(UDate date, UnicodeString& toAppendTo, FieldPosition& p
     UnicodeString str;
     
     // loop through the pattern string character by character
-    for (int32_t i = 0; i < fPattern.size() && U_SUCCESS(status); ++i) {
+    for (int32_t i = 0; i < fPattern.length() && U_SUCCESS(status); ++i) {
         UChar ch = fPattern[i];
         
         // Use subFormat() to format a repeated pattern character
         // when a different pattern or non-pattern character is seen
         if (ch != prevCh && count > 0) {
-            toAppendTo += subFormat(str, prevCh, count, toAppendTo.size(), pos, status);
+            toAppendTo += subFormat(str, prevCh, count, toAppendTo.length(), pos, status);
             count = 0;
         }
         if (ch == 0x0027 /*'\''*/) {
             // Consecutive single quotes are a single quote literal,
             // either outside of quotes or between quotes
-            if ((i+1) < fPattern.size() && fPattern[i+1] == 0x0027 /*'\''*/) {
+            if ((i+1) < fPattern.length() && fPattern[i+1] == 0x0027 /*'\''*/) {
                 toAppendTo += 0x0027 /*'\''*/;
                 ++i;
             } else {
@@ -438,7 +438,7 @@ SimpleDateFormat::format(UDate date, UnicodeString& toAppendTo, FieldPosition& p
 
     // Format the last item in the pattern, if any
     if (count > 0) {
-        toAppendTo += subFormat(str, prevCh, count, toAppendTo.size(), pos, status);
+        toAppendTo += subFormat(str, prevCh, count, toAppendTo.length(), pos, status);
     }
 
     // and if something failed (e.g., an invalid format character), reset our FieldPosition
@@ -659,7 +659,7 @@ SimpleDateFormat::subFormat(UnicodeString& result,
     if (pos.getField() == fgPatternIndexToDateFormatField[patternCharIndex]) {
         if (pos.getBeginIndex() == 0 && pos.getEndIndex() == 0) {
             pos.setBeginIndex(beginOffset);
-            pos.setEndIndex(beginOffset + result.size());
+            pos.setEndIndex(beginOffset + result.length());
         }
     }
     
@@ -730,7 +730,7 @@ SimpleDateFormat::parse(const UnicodeString& text, ParsePosition& pos) const
 
     // loop through the pattern string character by character, using it to control how
     // we match characters in the input
-    for (int32_t i = 0; i < fPattern.size();++i) {
+    for (int32_t i = 0; i < fPattern.length();++i) {
         UChar ch = fPattern[i];
         
         // if we're inside a quoted string, match characters exactly until we hit
@@ -746,7 +746,7 @@ SimpleDateFormat::parse(const UnicodeString& text, ParsePosition& pos) const
                 // a quote literal we need to match.
                 if (count == 0)
                 {
-                    if(start > text.size() || ch != text[start])
+                    if(start > text.length() || ch != text[start])
                         {
                             pos.setIndex(oldStart);
                             pos.setErrorIndex(start);
@@ -761,7 +761,7 @@ SimpleDateFormat::parse(const UnicodeString& text, ParsePosition& pos) const
             else
                 {
                     // pattern uses text following from 1st single quote.
-                    if (start >= text.size() || ch != text[start]) {
+                    if (start >= text.length() || ch != text[start]) {
                         // Check for cases like: 'at' in pattern vs "xt"
                         // in time text, where 'a' doesn't match with 'x'.
                         // If fail to match, return null.
@@ -801,7 +801,7 @@ SimpleDateFormat::parse(const UnicodeString& text, ParsePosition& pos) const
                         // for example, 'o''clock'.  We need to parse this as
                         // representing a single quote within the quote.
                         int32_t startOffset = start;
-                        if (start >= text.size() ||  ch != text[start])
+                        if (start >= text.length() ||  ch != text[start])
                         {
                             pos.setErrorIndex(startOffset);
                             pos.setIndex(oldStart);
@@ -857,7 +857,7 @@ SimpleDateFormat::parse(const UnicodeString& text, ParsePosition& pos) const
                     // {sfb} correct Date?
                     return 0;
                 }
-                if (start >= text.size() || ch != text[start]) {
+                if (start >= text.length() || ch != text[start]) {
                     // handle cases like: 'MMMM dd' in pattern vs. "janx20"
                     // in time text, where ' ' doesn't match with 'x'.
                     pos.setErrorIndex(start);
@@ -873,7 +873,7 @@ SimpleDateFormat::parse(const UnicodeString& text, ParsePosition& pos) const
             // otherwise, match characters exactly
             else 
             {
-                if (start >= text.size() || ch != text[start]) {
+                if (start >= text.length() || ch != text[start]) {
                     // handle cases like: 'MMMM   dd' in pattern vs.
                     // "jan,,,20" in time text, where "   " doesn't
                     // match with ",,,".
@@ -997,7 +997,7 @@ int32_t SimpleDateFormat::matchString(const UnicodeString& text,
 
     for (; i < count; ++i)
     {
-        int32_t length = data[i].size();
+        int32_t length = data[i].length();
         // Always compare if we have no match yet; otherwise only compare
         // against potentially better matches (longer strings).
 
@@ -1082,7 +1082,7 @@ int32_t SimpleDateFormat::subParse(const UnicodeString& text, int32_t& start, UC
     // If there are any spaces here, skip over them.  If we hit the end
     // of the string, then fail.
     for (;;) {
-        if (pos.getIndex() >= text.size()) 
+        if (pos.getIndex() >= text.length()) 
             return -start;
         UChar c = text[pos.getIndex()];
         if (c != 0x0020 /*' '*/ && c != 0x0009 /*'\t'*/) 
@@ -1104,7 +1104,7 @@ int32_t SimpleDateFormat::subParse(const UnicodeString& text, int32_t& start, UC
         // but that's going to be difficult.
         if (obeyCount)
         {
-            if ((start+count) > text.size()) 
+            if ((start+count) > text.length()) 
                 return -start;
             UnicodeString temp;
             text.extractBetween(0, start + count, temp);
@@ -1216,12 +1216,12 @@ int32_t SimpleDateFormat::subParse(const UnicodeString& text, int32_t& start, UC
         UnicodeString lcaseGMT(fgGmt);
         lcaseGMT.toLower();
         
-        if ((text.size() - start) > fgGmt.size() &&
-            (lcaseText.compare(start, lcaseGMT.size(), lcaseGMT, 0, lcaseGMT.size())) == 0)
+        if ((text.length() - start) > fgGmt.length() &&
+            (lcaseText.compare(start, lcaseGMT.length(), lcaseGMT, 0, lcaseGMT.length())) == 0)
         {
             fCalendar->set(Calendar::DST_OFFSET, 0);
 
-            pos.setIndex(start + fgGmt.size());
+            pos.setIndex(start + fgGmt.length());
 
             if( text[pos.getIndex()] == 0x002B /*'+'*/ )
                 sign = 1;
@@ -1285,7 +1285,7 @@ int32_t SimpleDateFormat::subParse(const UnicodeString& text, int32_t& start, UC
                     UnicodeString s2(fSymbols->fZoneStrings[i][j]);
                     s2.toLower();
                 
-                    if ((s1.compare(start, s2.size(), s2, 0, s2.size())) == 0)
+                    if ((s1.compare(start, s2.length(), s2, 0, s2.length())) == 0)
                         break;
                 }
                 if (j <= 4)
@@ -1296,7 +1296,7 @@ int32_t SimpleDateFormat::subParse(const UnicodeString& text, int32_t& start, UC
                     // use the correct DST SAVINGS for the zone.
                     delete tz;
                     fCalendar->set(Calendar::DST_OFFSET, j >= 3 ? U_MILLIS_PER_HOUR : 0);
-                    return (start + fSymbols->fZoneStrings[i][j].size());
+                    return (start + fSymbols->fZoneStrings[i][j].length());
                 }
             }
 
@@ -1367,7 +1367,7 @@ int32_t SimpleDateFormat::subParse(const UnicodeString& text, int32_t& start, UC
         // Handle "generic" fields
         if (obeyCount)
         {
-            if ((start+count) > text.size()) 
+            if ((start+count) > text.length()) 
                 return -start;
             UnicodeString s;
             // {sfb} old code had extract, make sure it works
@@ -1404,7 +1404,7 @@ void SimpleDateFormat::translatePattern(const UnicodeString& originalPattern,
   
   translatedPattern.remove();
   bool_t inQuote = FALSE;
-  for (UTextOffset i = 0; i < originalPattern.size(); ++i) {
+  for (UTextOffset i = 0; i < originalPattern.length(); ++i) {
     UChar c = originalPattern[i];
     if (inQuote) {
       if (c == 0x0027 /*'\''*/) 
diff --git a/icu4c/source/i18n/sortkey.cpp b/icu4c/source/i18n/sortkey.cpp
index f5f95fa147..e3ebcf6d53 100644
--- a/icu4c/source/i18n/sortkey.cpp
+++ b/icu4c/source/i18n/sortkey.cpp
@@ -229,7 +229,7 @@ int32_t
 CollationKey::storeUnicodeString(int32_t cursor, const UnicodeString &value)
 {
     UTextOffset input = 0;
-    int32_t charCount = value.size();
+    int32_t charCount = value.length();
 
     while (input < charCount)
     {
@@ -242,7 +242,7 @@ CollationKey::storeUnicodeString(int32_t cursor, const UnicodeString &value)
 CollationKey&
 CollationKey::copyUnicodeString(const UnicodeString &value)
 {
-    int32_t charCount = value.size();
+    int32_t charCount = value.length();
 
     // We allocate enough space for two null bytes at the end.
     ensureCapacity((charCount * 2) + 2);
diff --git a/icu4c/source/i18n/tblcoll.cpp b/icu4c/source/i18n/tblcoll.cpp
index 036efae5c4..82441b5c6e 100644
--- a/icu4c/source/i18n/tblcoll.cpp
+++ b/icu4c/source/i18n/tblcoll.cpp
@@ -553,7 +553,7 @@ RuleBasedCollator::RuleBasedCollator(   const Locale& desiredLocale,
     
   for (;;)
     {
-      if (localeName.size() == 0)
+      if (localeName.length() == 0)
     {
       if (next == eDone)
             {
@@ -949,8 +949,8 @@ RuleBasedCollator::compare( const UnicodeString& source,
     UnicodeString target_togo;
     UTextOffset begin=0;
 
-    source.extract(begin, icu_min(length,source.size()), source_togo);
-    target.extract(begin, icu_min(length,target.size()), target_togo);
+    source.extract(begin, icu_min(length,source.length()), source_togo);
+    target.extract(begin, icu_min(length,target.length()), target_togo);
     return (RuleBasedCollator::compare(source_togo, target_togo));
 }
 
@@ -1362,7 +1362,7 @@ RuleBasedCollator::getCollationKey( const   UnicodeString&  source,
                                     CollationKey&   sortkey,
                                     UErrorCode&      status) const
 {
-    return RuleBasedCollator::getCollationKey(source.getUChars(), source.size(), sortkey, status);
+    return RuleBasedCollator::getCollationKey(source.getUChars(), source.length(), sortkey, status);
 }
 
 CollationKey&
@@ -1466,7 +1466,7 @@ RuleBasedCollator::getCollationKey( const   UChar*  source,
 
         if (U_SUCCESS(status))
         {
-            totalIdent = decomp.size() + 1;
+            totalIdent = decomp.length() + 1;
         }
     }
 
@@ -1607,7 +1607,7 @@ RuleBasedCollator::build(const UnicodeString&   pattern,
     UnicodeString expChars;
     UnicodeString groupChars;
 
-    if (pattern.size() == 0)
+    if (pattern.length() == 0)
     {
         status = U_INVALID_FORMAT_ERROR;
         return;
@@ -1645,16 +1645,16 @@ RuleBasedCollator::build(const UnicodeString&   pattern,
             entry->getChars(groupChars);
 
             // check if french secondary needs to be turned on
-            if ((groupChars.size() > 1) &&
-                (groupChars[groupChars.size()-(T_INT32(1))] == 0x0040))
+            if ((groupChars.length() > 1) &&
+                (groupChars[groupChars.length()-(T_INT32(1))] == 0x0040))
             {
                 data->isFrenchSec = TRUE;
-                groupChars.remove(groupChars.size()-(T_INT32(1)));
+                groupChars.remove(groupChars.length()-(T_INT32(1)));
             }
 
             order = increment((Collator::ECollationStrength)entry->getStrength(), order);
 
-            if (entry->getExtension(expChars).size() != 0)
+            if (entry->getExtension(expChars).length() != 0)
             {
                 // encountered an expanding character, where one character on input
                 // expands to several sort elements (e.g. 'ö' --> 'o' 'e')
@@ -1664,7 +1664,7 @@ RuleBasedCollator::build(const UnicodeString&   pattern,
                     return;
                 }
             }
-            else if (groupChars.size() > 1)
+            else if (groupChars.length() > 1)
             {
                 // encountered a contracting character, where several characters on input
                 // contract into one sort order.  For example, "ch" is treated as a single
@@ -1750,7 +1750,7 @@ RuleBasedCollator::build(const UnicodeString&   pattern,
                 bool_t allThere = TRUE;
                 int32_t i;
 
-                for (i = 0; i < decomp.size(); i += 1)
+                for (i = 0; i < decomp.length(); i += 1)
                 {
                     if (getCharOrder(decomp[i]) == UNMAPPED)
                     {
@@ -1914,7 +1914,7 @@ RuleBasedCollator::addExpandOrder(  const   UnicodeString& contractChars,
     int32_t tableIndex = addExpansion(anOrder, expandChars);
     
     // And add its index into the main mapping table
-    if (contractChars.size() > 1)
+    if (contractChars.length() > 1)
     {
         addContractOrder(contractChars, tableIndex, status);
     }
@@ -1939,7 +1939,7 @@ int32_t RuleBasedCollator::addExpansion(int32_t anOrder, const UnicodeString &ex
     // If anOrder is valid, we want to add it at the beginning of the list
     int32_t offset = (anOrder == UNMAPPED) ? 0 : 1;
     
-    VectorOfInt *valueList = new VectorOfInt(expandChars.size() + offset);
+    VectorOfInt *valueList = new VectorOfInt(expandChars.length() + offset);
 
     if (offset == 1)
     {
@@ -1947,7 +1947,7 @@ int32_t RuleBasedCollator::addExpansion(int32_t anOrder, const UnicodeString &ex
     }
 
     int32_t i;
-    for (i = 0; i < expandChars.size(); i += 1)
+    for (i = 0; i < expandChars.length(); i += 1)
     {
         UChar ch = expandChars[i];
         int32_t mapValue = getCharOrder(ch);
@@ -2140,7 +2140,7 @@ RuleBasedCollator::hashCode() const
 {
     int32_t         value = 0;
     int32_t         c;
-    int32_t         count = getRules().size();
+    int32_t         count = getRules().length();
     UTextOffset      pos = count - 1;
 
     if (count > 64)
@@ -2410,7 +2410,7 @@ RuleBasedCollator::createPathName(  const UnicodeString&    prefix,
     workingName += name;
     workingName += suffix;
 
-    size = workingName.size();
+    size = workingName.length();
     returnVal = new char[size + 1];
     workingName.extract(0, size, returnVal, "");
     returnVal[size] = 0;
@@ -2425,7 +2425,7 @@ RuleBasedCollator::chopLocale(UnicodeString& localeName)
     // For instance, "de_CH" becomes "de", and "de" becomes "".
     // "" remains "".
 
-    int32_t     size = localeName.size();
+    int32_t     size = localeName.length();
     int32_t     i;
 
     for (i = size - 1; i > 0; i--)
diff --git a/icu4c/source/i18n/timezone.cpp b/icu4c/source/i18n/timezone.cpp
index 344d18d58d..f824132e43 100644
--- a/icu4c/source/i18n/timezone.cpp
+++ b/icu4c/source/i18n/timezone.cpp
@@ -537,7 +537,7 @@ TimeZone::createCustomTimeZone(const UnicodeString& id)
     UnicodeString idUppercase = id;
     idUppercase.toUpper();
 
-    if (id.size() > GMT_ID_LENGTH &&
+    if (id.length() > GMT_ID_LENGTH &&
         idUppercase.startsWith(GMT_ID))
     {
         ParsePosition pos(GMT_ID_LENGTH);
@@ -564,7 +564,7 @@ TimeZone::createCustomTimeZone(const UnicodeString& id)
         if (pos.getIndex() == start) return 0;
         offset = n.getLong();
 
-        if (pos.getIndex() < id.size() &&
+        if (pos.getIndex() < id.length() &&
             id[pos.getIndex()] == 0x003A /*':'*/)
         {
             // hh:mm
diff --git a/icu4c/source/i18n/ucol.cpp b/icu4c/source/i18n/ucol.cpp
index 9bfd326967..ace5e87e89 100644
--- a/icu4c/source/i18n/ucol.cpp
+++ b/icu4c/source/i18n/ucol.cpp
@@ -271,7 +271,7 @@ ucol_getRules(    const    UCollator        *coll,
         int32_t            *length)
 {
   const UnicodeString& rules = ((RuleBasedCollator*)coll)->getRules();
-  *length = rules.size();
+  *length = rules.length();
   return rules.getUChars();
 }
 
diff --git a/icu4c/source/i18n/umsg.cpp b/icu4c/source/i18n/umsg.cpp
index 6afab9ac08..5fd6c76c2e 100644
--- a/icu4c/source/i18n/umsg.cpp
+++ b/icu4c/source/i18n/umsg.cpp
@@ -51,10 +51,10 @@ findKeyword(const     UnicodeString&     s,
     // If so, the string contains a modifier, and we only want to 
     // parse the type
     int32_t commaPos = buffer.indexOf(0x002C);
-    commaPos = (commaPos == -1 ? buffer.size() : commaPos);
+    commaPos = (commaPos == -1 ? buffer.length() : commaPos);
     buffer.truncate(commaPos);
     if(buffer == list[i]) {
-      kwLen = list[i].size();
+      kwLen = list[i].length();
       return i;
     }
   }
diff --git a/icu4c/source/i18n/unum.cpp b/icu4c/source/i18n/unum.cpp
index 878defd011..d00201a5fb 100644
--- a/icu4c/source/i18n/unum.cpp
+++ b/icu4c/source/i18n/unum.cpp
@@ -538,12 +538,12 @@ unum_getSymbols(const UNumberFormat* fmt,
   syms->minusSign         = dfs->getMinusSign();
   
   dfs->getCurrencySymbol(temp);
-  len = icu_min(temp.size(), UNFSYMBOLSMAXSIZE);
+  len = icu_min(temp.length(), UNFSYMBOLSMAXSIZE);
   u_strncpy(syms->currency, temp.getUChars(), len);
   syms->currency[len > 0 ? len + 1 : 0] = 0x0000;
 
   dfs->getInternationalCurrencySymbol(temp);
-  len = icu_min(temp.size(), UNFSYMBOLSMAXSIZE);
+  len = icu_min(temp.length(), UNFSYMBOLSMAXSIZE);
   u_strncpy(syms->intlCurrency, temp.getUChars(), len);
   syms->intlCurrency[len > 0 ? len + 1 : 0] = 0x0000;
   
@@ -553,12 +553,12 @@ unum_getSymbols(const UNumberFormat* fmt,
   syms->padEscape       = dfs->getPadEscape();
 
   dfs->getInfinity(temp);
-  len = icu_min(temp.size(), UNFSYMBOLSMAXSIZE);
+  len = icu_min(temp.length(), UNFSYMBOLSMAXSIZE);
   u_strncpy(syms->infinity, temp.getUChars(), len);
   syms->infinity[len > 0 ? len + 1 : 0] = 0x0000;
 
   dfs->getNaN(temp);
-  len = icu_min(temp.size(), UNFSYMBOLSMAXSIZE);
+  len = icu_min(temp.length(), UNFSYMBOLSMAXSIZE);
   u_strncpy(syms->naN, temp.getUChars(), len);
   syms->naN[len > 0 ? len + 1 : 0] = 0x0000;
 }
diff --git a/icu4c/source/test/intltest/apicoll.cpp b/icu4c/source/test/intltest/apicoll.cpp
index 572d10212e..d657c071bb 100644
--- a/icu4c/source/test/intltest/apicoll.cpp
+++ b/icu4c/source/test/intltest/apicoll.cpp
@@ -129,7 +129,7 @@ CollationAPITest::TestProperty( char* par )
 
     logln("Default collation property test ended.");
     logln("Collator::getRules() testing ...");  
-    doAssert(((RuleBasedCollator*)col)->getRules().size() != 0, "getRules() result incorrect" );                
+    doAssert(((RuleBasedCollator*)col)->getRules().length() != 0, "getRules() result incorrect" );                
     logln("getRules tests end.");
 
     delete col; col = 0;
diff --git a/icu4c/source/test/intltest/citrtest.cpp b/icu4c/source/test/intltest/citrtest.cpp
index 7cef3b5db8..b46d1da753 100644
--- a/icu4c/source/test/intltest/citrtest.cpp
+++ b/icu4c/source/test/intltest/citrtest.cpp
@@ -89,12 +89,12 @@ void CharIterTest::TestIteration() {
         c = iter.first();
         i = 0;
 
-        if (iter.startIndex() != 0 || iter.endIndex() != text.size())
+        if (iter.startIndex() != 0 || iter.endIndex() != text.length())
             errln("startIndex() or endIndex() failed");
 
         logln("Testing forward iteration...");
         do {
-            if (c == CharacterIterator::DONE && i != text.size())
+            if (c == CharacterIterator::DONE && i != text.length())
                 errln("Iterator reached end prematurely");
             else if (c != text[i])
                 errln((UnicodeString)"Character mismatch at position " + i +
@@ -113,7 +113,7 @@ void CharIterTest::TestIteration() {
         } while (c != CharacterIterator::DONE);
 
         c = iter.last();
-        i = text.size() - 1;
+        i = text.length() - 1;
 
         logln("Testing backward iteration...");
         do {
diff --git a/icu4c/source/test/intltest/cppcnvt.cpp b/icu4c/source/test/intltest/cppcnvt.cpp
index 81c19e6352..11b9738621 100644
--- a/icu4c/source/test/intltest/cppcnvt.cpp
+++ b/icu4c/source/test/intltest/cppcnvt.cpp
@@ -477,7 +477,7 @@ void ConvertTest::TestConvert()
     
     logln("\n---Testing UChar* RoundTrip ...");
    // uniString3->remove();
-    uniString3->replace(0, uniString3->size(), my_ucs_file_buffer, i);
+    uniString3->replace(0, uniString3->length(), my_ucs_file_buffer, i);
     //uniString3 = new UnicodeString(my_ucs_file_buffer,i);
     
     /*checks if Uni1 == Uni3*/ 
@@ -499,7 +499,7 @@ void ConvertTest::TestConvert()
 
 
     SJIS.toUnicodeString(myString, mySJIS, 12, err);
-    if (U_FAILURE(err)||(myString.size()!=10)) errln("toUnicodeString test failed");
+    if (U_FAILURE(err)||(myString.length()!=10)) errln("toUnicodeString test failed");
     else logln("toUnicodeString test ok");
 
     fclose(ucs_file_in);    
@@ -516,7 +516,7 @@ void ConvertTest::TestConvert()
 
 void WriteToFile(const UnicodeString *a, FILE *myfile)
 {
-      uint32_t  size    =   a->size();
+      uint32_t  size    =   a->length();
       uint16_t  i       =   0;
       UChar   b       =   0xFEFF;
 
diff --git a/icu4c/source/test/intltest/dtfmrgts.cpp b/icu4c/source/test/intltest/dtfmrgts.cpp
index bba744d07a..8ba2be1f0d 100644
--- a/icu4c/source/test/intltest/dtfmrgts.cpp
+++ b/icu4c/source/test/intltest/dtfmrgts.cpp
@@ -189,7 +189,7 @@ void DateFormatRegressionTest::Test4052408()
                          pos.getBeginIndex() + ", " +
                          pos.getEndIndex());
         UnicodeString exp = expected[i];
-        if((exp.size() == 0 && str.size() == 0) || str == exp)
+        if((exp.length() == 0 && str.length() == 0) || str == exp)
             logln(" ok");
         else {
             logln(UnicodeString(" expected ") + exp);
diff --git a/icu4c/source/test/intltest/dtfmtrtts.cpp b/icu4c/source/test/intltest/dtfmtrtts.cpp
index d97141753c..1c3ec37b1c 100644
--- a/icu4c/source/test/intltest/dtfmtrtts.cpp
+++ b/icu4c/source/test/intltest/dtfmtrtts.cpp
@@ -305,7 +305,7 @@ int32_t DateFormatRoundTripTest::getField(UDate d, int32_t f) {
 UnicodeString& DateFormatRoundTripTest::escape(const UnicodeString& src, UnicodeString& dst ) 
 {
     dst.remove();
-    for (int32_t i = 0; i < src.size(); ++i) {
+    for (int32_t i = 0; i < src.length(); ++i) {
         UChar c = src[i];
         if(c < 0x0080) 
             dst += c;
diff --git a/icu4c/source/test/intltest/dtfmttst.cpp b/icu4c/source/test/intltest/dtfmttst.cpp
index 9b282dd9f2..f30cbc1afe 100644
--- a/icu4c/source/test/intltest/dtfmttst.cpp
+++ b/icu4c/source/test/intltest/dtfmttst.cpp
@@ -114,7 +114,7 @@ void DateFormatTest::TestWallyWedel()
         {
             //fmtDstOffset = fmtOffset->substring(3);
             fmtDstOffset = new UnicodeString();
-            fmtOffset.extract(3, fmtOffset.size(), *fmtDstOffset);
+            fmtOffset.extract(3, fmtOffset.length(), *fmtDstOffset);
         }
         /*
          * Show our result.
@@ -193,7 +193,7 @@ UnicodeString&
 DateFormatTest::escape(UnicodeString& s)
 {
     UnicodeString buf;
-    for (int32_t i=0; i<s.size(); ++i)
+    for (int32_t i=0; i<s.length(); ++i)
     {
         UChar c = s[(UTextOffset)i];
         if (c <= (UChar)0x7F) buf += c;
@@ -579,7 +579,7 @@ DateFormatTest::TestQuotePattern161()
     UnicodeString dateString; ((DateFormat*)formatter)->format(currentTime_1, dateString);
     UnicodeString exp("08/13/1997 at 10:42:28 AM ");
     logln((UnicodeString)"format(" + dateToString(currentTime_1) + ") = " + dateString);
-    if (0 != dateString.compareBetween(0, exp.size(), exp, 0, exp.size())) errln((UnicodeString)"FAIL: Expected " + exp);
+    if (0 != dateString.compareBetween(0, exp.length(), exp, 0, exp.length())) errln((UnicodeString)"FAIL: Expected " + exp);
     delete formatter;
     if (U_FAILURE(status)) errln((UnicodeString)"FAIL: UErrorCode received during test: " + (int32_t)status);
 }
@@ -621,7 +621,7 @@ DateFormatTest::TestBadInput135()
                     {
                         UnicodeString format; full->format(when, format);
                         logln(prefix + "OK: " + format);
-                        if (0!=format.compareBetween(0, expected.size(), expected, 0, expected.size()))
+                        if (0!=format.compareBetween(0, expected.length(), expected, 0, expected.length()))
                             errln((UnicodeString)"FAIL: Expected " + expected);
                     }
                 //}
@@ -708,7 +708,7 @@ DateFormatTest::TestBadInput135a()
       if (parsePosition.getIndex() != 0) {
     UnicodeString s1, s2;
     s.extract(0, parsePosition.getIndex(), s1);
-    s.extract(parsePosition.getIndex(), s.size(), s2);
+    s.extract(parsePosition.getIndex(), s.length(), s2);
     if (date == 0) errln((UnicodeString)"ERROR: null result fmt=\"" +
                  parseFormats[index] +
                  "\" pos=" + parsePosition.getIndex() + " " +
diff --git a/icu4c/source/test/intltest/intltest.cpp b/icu4c/source/test/intltest/intltest.cpp
index 7d21f4f9f7..eafabb9034 100644
--- a/icu4c/source/test/intltest/intltest.cpp
+++ b/icu4c/source/test/intltest/intltest.cpp
@@ -300,7 +300,7 @@ IntlTest::prettify(const UnicodeString &source,
   target.remove();
   target += "\"";
   
-  for (i = 0; i < source.size(); i += 1)
+  for (i = 0; i < source.length(); i += 1)
     {
       UChar ch = source[i];
 
@@ -710,7 +710,7 @@ void IntlTest::LL_message( UnicodeString message, bool_t newline )
     int32_t        saveFlags = stream.flags();
     stream << hex;
 
-    int32_t len = message.size();
+    int32_t len = message.length();
     UTextOffset pos = 0;
     bool_t gen = FALSE;
     do{
diff --git a/icu4c/source/test/intltest/itercoll.cpp b/icu4c/source/test/intltest/itercoll.cpp
index 486073c094..1b7c25a547 100644
--- a/icu4c/source/test/intltest/itercoll.cpp
+++ b/icu4c/source/test/intltest/itercoll.cpp
@@ -129,12 +129,12 @@ void CollationIteratorTest::TestOffset(char *par)
 
     int32_t offset = iter->getOffset();
 
-    if (offset != test1.size())
+    if (offset != test1.length())
     {
         UnicodeString msg1("offset at end != length: ");
         UnicodeString msg2(" vs ");
 
-        errln(msg1 + offset + msg2 + test1.size());
+        errln(msg1 + offset + msg2 + test1.length());
     }
 
     // Now set the offset back to the beginning and see if it works
diff --git a/icu4c/source/test/intltest/ittxtbd.cpp b/icu4c/source/test/intltest/ittxtbd.cpp
index f915bf4fc4..f5e07168a2 100644
--- a/icu4c/source/test/intltest/ittxtbd.cpp
+++ b/icu4c/source/test/intltest/ittxtbd.cpp
@@ -752,14 +752,14 @@ void IntlTestTextBoundary::TestLineInvariants()
     // it doesn't break around the non-breaking characters
     UnicodeString noBreak = CharsToUnicodeString("\\u00a0\\u2007\\u2011\\ufeff");
     UnicodeString work("aaa");
-    for (i = 0; i < testChars.size(); i++) {
+    for (i = 0; i < testChars.length(); i++) {
         UChar c = testChars[i];
         if (c == '\r' || c == '\n' || c == 0x2029 || c == 0x2028 || c == 0x0003)
             continue;
         work[0] = c;
-        for (j = 0; j < noBreak.size(); j++) {
+        for (j = 0; j < noBreak.length(); j++) {
             work[1] = noBreak[j];
-            for (k = 0; k < testChars.size(); k++) {
+            for (k = 0; k < testChars.length(); k++) {
                 work[2] = testChars[k];
                 e->setText(&work);
                 for (int l = e->first(); l != BreakIterator::DONE; l = e->next())
@@ -777,11 +777,11 @@ void IntlTestTextBoundary::TestLineInvariants()
     // it does break after hyphens (unless they're followed by a digit, a non-spacing mark,
     // a currency symbol, a non-breaking space, or a line or paragraph separator)
     UnicodeString dashes = CharsToUnicodeString("-\\u00ad\\u2010\\u2012\\u2013\\u2014");
-    for (i = 0; i < testChars.size(); i++) {
+    for (i = 0; i < testChars.length(); i++) {
         work[0] = testChars[i];
-        for (j = 0; j < dashes.size(); j++) {
+        for (j = 0; j < dashes.length(); j++) {
             work[1] = dashes[j];
-            for (k = 0; k < testChars.size(); k++) {
+            for (k = 0; k < testChars.length(); k++) {
                 UChar c = testChars[k];
                 if (Unicode::getType(c) == Unicode::DECIMAL_DIGIT_NUMBER ||
                     Unicode::getType(c) == Unicode::OTHER_NUMBER ||
@@ -915,7 +915,7 @@ void IntlTestTextBoundary::TestJapaneseLineBreak()
 
     UTextOffset i;
 
-    for (i = 0; i < precedingChars.size(); i++) {
+    for (i = 0; i < precedingChars.length(); i++) {
         testString[1] = precedingChars[i];
         iter->adoptText(it);
         int32_t j = iter->first();
@@ -931,7 +931,7 @@ void IntlTestTextBoundary::TestJapaneseLineBreak()
                         + "' (" + ((int)(precedingChars[i])) + ")");
     }
 
-    for (i = 0; i < followingChars.size(); i++) {
+    for (i = 0; i < followingChars.length(); i++) {
         testString[1] = followingChars[i];
         it = new StringCharacterIterator(testString);
         iter->adoptText(it);
@@ -1053,7 +1053,7 @@ void IntlTestTextBoundary::doForwardSelectionTest(BreakIterator& iterator,
     CharacterIterator *itSource = 0;
     CharacterIterator *itTarget = 0;
 
-    logln("doForwardSelectionTest text of length: "+testText.size());
+    logln("doForwardSelectionTest text of length: "+testText.length());
 
     // check to make sure setText() and getText() work right
     iterator.setText(&testText);
@@ -1074,7 +1074,7 @@ void IntlTestTextBoundary::doForwardSelectionTest(BreakIterator& iterator,
             errln((UnicodeString)"current() failed: it returned " + iterator.current() + " and offset was " + offset);
 
         expectedResult = result->elementAt(forwardSelectionCounter);
-        forwardSelectionOffset += expectedResult.size();
+        forwardSelectionOffset += expectedResult.length();
         testText.extractBetween(lastOffset, offset, selectionResult);
         if (offset != forwardSelectionOffset) {
             errln((UnicodeString)"\n*** Selection #" +
@@ -1082,11 +1082,11 @@ void IntlTestTextBoundary::doForwardSelectionTest(BreakIterator& iterator,
                   "\nExpected : " +
                   expectedResult +
                   " - length : " +
-                  expectedResult.size() +
+                  expectedResult.length() +
                   "\nSelected : " +
                   selectionResult +
                   " - length : " +
-                  selectionResult.size());
+                  selectionResult.length());
         }
         logln((UnicodeString)"#" + forwardSelectionCounter + " ["+lastOffset+", "+offset+"] : " + selectionResult);
 
@@ -1105,7 +1105,7 @@ void IntlTestTextBoundary::doBackwardSelectionTest(BreakIterator& iterator,
                                                    Vector* result)
 {
     int32_t backwardSelectionCounter = (result->size() - 1);
-    int32_t neededOffset = testText.size();
+    int32_t neededOffset = testText.length();
     int32_t lastOffset = iterator.last();
     iterator.setText(&testText);
     int32_t offset = iterator.previous();
@@ -1116,7 +1116,7 @@ void IntlTestTextBoundary::doBackwardSelectionTest(BreakIterator& iterator,
     while(offset != BreakIterator::DONE)
     {
         expectedResult = (UnicodeString)result->elementAt(backwardSelectionCounter);
-        neededOffset -= expectedResult.size();
+        neededOffset -= expectedResult.length();
         testText.extractBetween(offset, lastOffset, selectionResult);
         if(offset != neededOffset) {
             errln(
@@ -1161,16 +1161,16 @@ void IntlTestTextBoundary::doFirstSelectionTest(BreakIterator& iterator,
                 "\nExpexcted : " +
                 expectedFirstSelection +
                 " - length : " +
-                expectedFirstSelection.size() +
+                expectedFirstSelection.length() +
                 "\nSelected : " +
                 tempFirst +
                 " - length : " +
-                tempFirst.size() +
+                tempFirst.length() +
                 "\n");
             success = FALSE;
         }
     }
-    else if (selectionStart != 0 || testText.size() != 0) {
+    else if (selectionStart != 0 || testText.length() != 0) {
         errln((UnicodeString)"\n### Error in TTestFindWord::doFirstSelectionTest. Could not get first selection.\n"+
             "start = "+selectionStart+"  end = "+selectionEnd);
         success = FALSE;
@@ -1208,16 +1208,16 @@ void IntlTestTextBoundary::doLastSelectionTest(BreakIterator& iterator,
                 "\nExpexcted : " +
                 expectedLastSelection +
                 " - length : " +
-                expectedLastSelection.size() +
+                expectedLastSelection.length() +
                 "\nSelected : " +
                  tempLast +
                  " - length : " +
-                tempLast.size() +
+                tempLast.length() +
                  "\n");
             success = FALSE;
         }
     }
-    else if (selectionEnd != 0 || testText.size() != 0) {
+    else if (selectionEnd != 0 || testText.length() != 0) {
         errln((UnicodeString)"\n### Error in TTestFindWord::doLastSelectionTest. Could not get last selection."+
             "["+selectionStart+","+selectionEnd+"]");
         success = FALSE;
@@ -1242,7 +1242,7 @@ void IntlTestTextBoundary::doForwardIndexSelectionTest(BreakIterator& iterator,
                                                        Vector* result)
 {
     int32_t arrayCount = result->size();
-    int32_t textLength = testText.size();
+    int32_t textLength = testText.length();
     iterator.setText(&testText);
     for(UTextOffset offset = 0; offset < textLength; offset++) {
         int32_t selBegin = iterator.preceding(offset);
@@ -1253,7 +1253,7 @@ void IntlTestTextBoundary::doForwardIndexSelectionTest(BreakIterator& iterator,
         int32_t pos = 0;
         if (selBegin != BreakIterator::DONE) {
             while (pos < selBegin && entry < arrayCount) {
-                pos += ((UnicodeString)(result->elementAt(entry))).size();
+                pos += ((UnicodeString)(result->elementAt(entry))).length();
                 ++entry;
             }
             if (pos != selBegin) {
@@ -1261,7 +1261,7 @@ void IntlTestTextBoundary::doForwardIndexSelectionTest(BreakIterator& iterator,
                 continue;
             }
             else {
-                pos += ((UnicodeString)(result->elementAt(entry))).size();
+                pos += ((UnicodeString)(result->elementAt(entry))).length();
                 ++entry;
             }
         }
@@ -1271,7 +1271,7 @@ void IntlTestTextBoundary::doForwardIndexSelectionTest(BreakIterator& iterator,
                 continue;
             }
             else {
-                pos += ((UnicodeString)(result->elementAt(entry))).size();
+                pos += ((UnicodeString)(result->elementAt(entry))).length();
                 ++entry;
             }
         }
@@ -1290,7 +1290,7 @@ void IntlTestTextBoundary::doBackwardIndexSelectionTest(BreakIterator& iterator,
                                                         Vector* result)
 {
     int32_t arrayCount = result->size();
-    int32_t textLength = testText.size();
+    int32_t textLength = testText.length();
     iterator.setText(&testText);
     for(UTextOffset offset = textLength - 1; offset >= 0; offset--) {
         int32_t selBegin = iterator.preceding(offset);
@@ -1301,7 +1301,7 @@ void IntlTestTextBoundary::doBackwardIndexSelectionTest(BreakIterator& iterator,
         int32_t pos = 0;
         if (selBegin != BreakIterator::DONE) {
             while (pos < selBegin && entry < arrayCount) {
-                pos += ((UnicodeString)(result->elementAt(entry))).size();
+                pos += ((UnicodeString)(result->elementAt(entry))).length();
                 ++entry;
             }
             if (pos != selBegin) {
@@ -1309,7 +1309,7 @@ void IntlTestTextBoundary::doBackwardIndexSelectionTest(BreakIterator& iterator,
                 continue;
             }
             else {
-                pos += ((UnicodeString)(result->elementAt(entry))).size();
+                pos += ((UnicodeString)(result->elementAt(entry))).length();
                 ++entry;
             }
         }
@@ -1319,7 +1319,7 @@ void IntlTestTextBoundary::doBackwardIndexSelectionTest(BreakIterator& iterator,
                 continue;
             }
             else {
-                pos += ((UnicodeString)(result->elementAt(entry))).size();
+                pos += ((UnicodeString)(result->elementAt(entry))).length();
                 ++entry;
             }
         }
@@ -1337,7 +1337,7 @@ void IntlTestTextBoundary::TestBug4153072() {
     BreakIterator *iter = BreakIterator::createWordInstance();
     UnicodeString str("...Hello, World!...");
     int32_t begin = 3;
-    int32_t end = str.size() - 3;
+    int32_t end = str.length() - 3;
     bool_t gotException = FALSE;
     bool_t dummy;
 
@@ -1363,7 +1363,7 @@ void IntlTestTextBoundary::doMultipleSelectionTest(BreakIterator& iterator,
     int32_t testOffset;
     int32_t count = 0;
 
-    logln("doMultipleSelectionTest text of length: "+testText.size());
+    logln("doMultipleSelectionTest text of length: "+testText.length());
 
     if (*testIterator != iterator)
         errln("clone() or operator!= failed: two clones compared unequal");
@@ -1410,11 +1410,11 @@ void IntlTestTextBoundary::doBreakInvariantTest(BreakIterator& tb, UnicodeString
     UnicodeString breaks = CharsToUnicodeString("\r\n\\u2029\\u2028");
     UTextOffset i, j;
 
-    for (i = 0; i < breaks.size(); i++) {
+    for (i = 0; i < breaks.length(); i++) {
         work[1] = breaks[i];
-        for (j = 0; j < testChars.size(); j++) {
+        for (j = 0; j < testChars.length(); j++) {
             work[0] = testChars[j];
-            for (int k = 0; k < testChars.size(); k++) {
+            for (int k = 0; k < testChars.length(); k++) {
                 UChar c = testChars[k];
 
                 // if a cr is followed by lf, ps, ls or etx, don't do the check (that's
@@ -1449,9 +1449,9 @@ void IntlTestTextBoundary::doOtherInvariantTest(BreakIterator& tb, UnicodeString
     UTextOffset i, j;
 
     // a break should never occur between CR and LF
-    for (i = 0; i < testChars.size(); i++) {
+    for (i = 0; i < testChars.length(); i++) {
         work[0] = testChars[i];
-        for (j = 0; j < testChars.size(); j++) {
+        for (j = 0; j < testChars.length(); j++) {
             work[3] = testChars[j];
             tb.setText(&work);
             for (int32_t k = tb.first(); k != BreakIterator::DONE; k = tb.next())
@@ -1469,12 +1469,12 @@ void IntlTestTextBoundary::doOtherInvariantTest(BreakIterator& tb, UnicodeString
     // character is CR, LF, PS, or LS
     work.remove();
     work += "aaaa";
-    for (i = 0; i < testChars.size(); i++) {
+    for (i = 0; i < testChars.length(); i++) {
         UChar c = testChars[i];
         if (c == '\n' || c == '\r' || c == 0x2029 || c == 0x2028 || c == 0x0003)
             continue;
         work[1] = c;
-        for (j = 0; j < testChars.size(); j++) {
+        for (j = 0; j < testChars.length(); j++) {
             c = testChars[j];
             if ((Unicode::getType(c) != Unicode::NON_SPACING_MARK) && 
                 (Unicode::getType(c) != Unicode::ENCLOSING_MARK))
@@ -1500,7 +1500,7 @@ void IntlTestTextBoundary::sample(BreakIterator& tb,
     UnicodeString   substring;
     bool_t verboseWas = verbose;
     verbose = TRUE;
-    logln("-------------------------"+title+" length = "+text.size());
+    logln("-------------------------"+title+" length = "+text.length());
     tb.setText(&text);
     int32_t start = tb.first();
     int32_t end;
diff --git a/icu4c/source/test/intltest/loctest.cpp b/icu4c/source/test/intltest/loctest.cpp
index b0c9a1c921..dd21232f30 100644
--- a/icu4c/source/test/intltest/loctest.cpp
+++ b/icu4c/source/test/intltest/loctest.cpp
@@ -151,7 +151,7 @@ void LocaleTest::TestBasicGetters() {
         if (testLocale.getCountry(temp) != (dataTable[CTRY][i]))
             errln("  Country code mismatch: " + temp + " versus "
                         + dataTable[CTRY][i]);
-        if (testLocale.getVariant(temp).size() != 0)
+        if (testLocale.getVariant(temp).length() != 0)
             errln("  Variant code mismatch: " + temp + " versus \"\"");
     }
 
@@ -496,27 +496,27 @@ void LocaleTest::doTestDisplayNames(Locale& inLocale,
         UnicodeString  expectedName;
 
         expectedLang = dataTable[compareIndex][i];
-        if (expectedLang.size() == 0 && defaultIsFrench)
+        if (expectedLang.length() == 0 && defaultIsFrench)
             expectedLang = dataTable[DLANG_FR][i];
-        if (expectedLang.size() == 0)
+        if (expectedLang.length() == 0)
             expectedLang = dataTable[DLANG_EN][i];
 
         expectedCtry = dataTable[compareIndex + 1][i];
-        if (expectedCtry.size() == 0 && defaultIsFrench)
+        if (expectedCtry.length() == 0 && defaultIsFrench)
             expectedCtry = dataTable[DCTRY_FR][i];
-        if (expectedCtry.size() == 0)
+        if (expectedCtry.length() == 0)
             expectedCtry = dataTable[DCTRY_EN][i];
 
         expectedVar = dataTable[compareIndex + 2][i];
-        if (expectedVar.size() == 0 && defaultIsFrench)
+        if (expectedVar.length() == 0 && defaultIsFrench)
             expectedVar = dataTable[DVAR_FR][i];
-        if (expectedVar.size() == 0)
+        if (expectedVar.length() == 0)
             expectedVar = dataTable[DVAR_EN][i];
 
         expectedName = dataTable[compareIndex + 3][i];
-        if (expectedName.size() == 0 && defaultIsFrench)
+        if (expectedName.length() == 0 && defaultIsFrench)
             expectedName = dataTable[DNAME_FR][i];
-        if (expectedName.size() == 0)
+        if (expectedName.length() == 0)
             expectedName = dataTable[DNAME_EN][i];
 
         if (testLang != expectedLang)
@@ -703,7 +703,7 @@ LocaleTest::TestGetLangsAndCountries()
         UnicodeString lc(test[i]);
         if (test[i] != lc.toLower())
             errln(test[i] + " is not all lower case.");
-        if (test[i].size() != 2)
+        if (test[i].length() != 2)
             errln(test[i] + " is not two characters long.");
         if (i > 0 && test[i].compare(test[i - 1]) <= 0)
             errln(test[i] + " appears in an out-of-order position in the list.");
@@ -732,7 +732,7 @@ LocaleTest::TestGetLangsAndCountries()
         UnicodeString uc(test[i]);
         if (test[i] != uc.toUpper())
             errln(test[i] + " is not all upper case.");
-        if (test[i].size() != 2)
+        if (test[i].length() != 2)
             errln(test[i] + " is not two characters long.");
         if (i > 0 && test[i].compare(test[i - 1]) <= 0)
             errln(test[i] + " appears in an out-of-order position in the list.");
diff --git a/icu4c/source/test/intltest/nmfmtrt.cpp b/icu4c/source/test/intltest/nmfmtrt.cpp
index e63e6ae7b1..ce562a47d2 100644
--- a/icu4c/source/test/intltest/nmfmtrt.cpp
+++ b/icu4c/source/test/intltest/nmfmtrt.cpp
@@ -292,7 +292,7 @@ NumberFormatRoundTripTest::escape(UnicodeString& s)
 {
     UnicodeString copy(s);
     s.remove();
-    for(int i = 0; i < copy.size(); ++i) {
+    for(int i = 0; i < copy.length(); ++i) {
         UChar c = copy[i];
         if(c < 0x00FF) 
             s += c;
diff --git a/icu4c/source/test/intltest/numfmtst.cpp b/icu4c/source/test/intltest/numfmtst.cpp
index 551b217fcc..9782d0405c 100644
--- a/icu4c/source/test/intltest/numfmtst.cpp
+++ b/icu4c/source/test/intltest/numfmtst.cpp
@@ -157,7 +157,7 @@ NumberFormatTest::TestExponential()
             if (af.getType() == Formattable::kLong) a = af.getLong();
             else if (af.getType() == Formattable::kDouble) a = af.getDouble();
             else errln((UnicodeString)"FAIL: Non-numeric Formattable returned");
-            if (pos.getIndex() == s.size())
+            if (pos.getIndex() == s.length())
             {
                 logln((UnicodeString)"  -parse-> " + a);
                 if (a != valParse[v+ival])
@@ -179,7 +179,7 @@ NumberFormatTest::TestExponential()
             int32_t a;
             if (af.getType() == Formattable::kLong) a = af.getLong();
             else errln((UnicodeString)"FAIL: Non-long Formattable returned");
-            if (pos.getIndex() == s.size())
+            if (pos.getIndex() == s.length())
             {
                 logln((UnicodeString)"  -parse-> " + a);
                 if (a != lvalParse[v+ilval])
@@ -269,7 +269,7 @@ UnicodeString&
 NumberFormatTest::escape(UnicodeString& s)
 {
     UnicodeString buf;
-    for (int32_t i=0; i<s.size(); ++i)
+    for (int32_t i=0; i<s.length(); ++i)
     {
         UChar c = s[(UTextOffset)i];
         if (c <= (UChar)0x7F) buf += c;
diff --git a/icu4c/source/test/intltest/numrgts.cpp b/icu4c/source/test/intltest/numrgts.cpp
index 2bcd63814d..c6c301278c 100644
--- a/icu4c/source/test/intltest/numrgts.cpp
+++ b/icu4c/source/test/intltest/numrgts.cpp
@@ -121,7 +121,7 @@ static UnicodeString str(const char *input)
   
   while ((index = result.indexOf("\\u")) != -1)
     {
-      if (index + 6 <= result.size())
+      if (index + 6 <= result.length())
     {
       UChar c = 0;
       for (int i = index + 2; i < index + 6; i++) {
@@ -258,11 +258,11 @@ void NumberFormatRegressionTest::Test4087535 ()
     UnicodeString buffer;
     FieldPosition pos(FieldPosition::DONT_CARE);
     buffer = df->format(n, buffer, pos);
-    if (buffer.size() == 0)
+    if (buffer.length() == 0)
         errln(/*n + */": '" + buffer + "'");
     n = 0.1;
     buffer = df->format(n, buffer, pos);
-    if (buffer.size() == 0)
+    if (buffer.length() == 0)
         errln(/*n + */": '" + buffer + "'");
 
     delete df;
@@ -1445,16 +1445,16 @@ void NumberFormatRegressionTest::Test4122840()
             symbols->setDecimalSeparator(symbols->getMonetaryDecimalSeparator());
             
             UnicodeString buf(pattern);
-            for (int j = 0; j < buf.size(); j++) {
+            for (int j = 0; j < buf.length(); j++) {
                 if (buf[j] == 0x00a4 ) {
                     if(buf[j + 1] == 0x00a4) {
                         // {sfb} added to support double currency marker (intl currency sign)
                         buf.replace(j, /*j+*/2, symbols->getInternationalCurrencySymbol(temp)); 
-                        j += symbols->getInternationalCurrencySymbol(temp).size() - 1 + 1;
+                        j += symbols->getInternationalCurrencySymbol(temp).length() - 1 + 1;
                     }
                     else {
                         buf.replace(j, /*j+*/1, symbols->getCurrencySymbol(temp)); 
-                        j += symbols->getCurrencySymbol(temp).size() - 1;
+                        j += symbols->getCurrencySymbol(temp).length() - 1;
                     }                    
                 }
             }
diff --git a/icu4c/source/test/intltest/transtst.cpp b/icu4c/source/test/intltest/transtst.cpp
index 224d02c435..4c268ac1ed 100644
--- a/icu4c/source/test/intltest/transtst.cpp
+++ b/icu4c/source/test/intltest/transtst.cpp
@@ -524,7 +524,7 @@ static UChar toHexString(int32_t i) { return i + (i < 10 ? '0' : ('A' - 10)); }
 UnicodeString
 TransliteratorTest::escape(const UnicodeString& s) {
     UnicodeString buf;
-    for (int32_t i=0; i<s.size(); ++i)
+    for (int32_t i=0; i<s.length(); ++i)
     {
         UChar c = s[(UTextOffset)i];
         if (' ' <= c && c <= (UChar)0x7F) {
diff --git a/icu4c/source/test/intltest/tsmthred.cpp b/icu4c/source/test/intltest/tsmthred.cpp
index f025f6ad77..daf088b504 100644
--- a/icu4c/source/test/intltest/tsmthred.cpp
+++ b/icu4c/source/test/intltest/tsmthred.cpp
@@ -444,11 +444,11 @@ UnicodeString showDifference(const UnicodeString& expected, const UnicodeString&
 {
     UnicodeString res;
     res = expected + "<Expected\n";
-    if(expected.size() != result.size())
+    if(expected.length() != result.length())
         res += " [ Different lengths ] \n";
     else
     {
-        for(int32_t i=0;i<expected.size();i++)
+        for(int32_t i=0;i<expected.length();i++)
         {
             if(expected[i] == result[i])
             {
diff --git a/icu4c/source/test/intltest/tstnorm.cpp b/icu4c/source/test/intltest/tstnorm.cpp
index 298271c62b..3c05f57314 100644
--- a/icu4c/source/test/intltest/tstnorm.cpp
+++ b/icu4c/source/test/intltest/tstnorm.cpp
@@ -33,7 +33,7 @@ static UnicodeString str(const char *input)
   
   while ((index = result.indexOf("\\u")) != -1)
     {
-      if (index + 6 <= result.size())
+      if (index + 6 <= result.length())
     {
       UChar c = 0;
       for (int i = index + 2; i < index + 6; i++) {
@@ -267,7 +267,7 @@ UnicodeString BasicNormalizerTest::hex(UChar ch) {
 
 UnicodeString BasicNormalizerTest::hex(const UnicodeString& s) {
     UnicodeString result;
-    for (int i = 0; i < s.size(); ++i) {
+    for (int i = 0; i < s.length(); ++i) {
         if (i != 0) result += ',';
         appendHex(s[i], 4, result);
     }
diff --git a/icu4c/source/test/intltest/usettest.cpp b/icu4c/source/test/intltest/usettest.cpp
index 2edef19caa..67caf3c558 100644
--- a/icu4c/source/test/intltest/usettest.cpp
+++ b/icu4c/source/test/intltest/usettest.cpp
@@ -129,7 +129,7 @@ static UChar toHexString(int32_t i) { return i + (i < 10 ? '0' : ('A' - 10)); }
 UnicodeString
 UnicodeSetTest::escape(const UnicodeString& s) {
     UnicodeString buf;
-    for (int32_t i=0; i<s.size(); ++i)
+    for (int32_t i=0; i<s.length(); ++i)
     {
         UChar c = s[(UTextOffset)i];
         if (' ' <= c && c <= (UChar)0x7F) {
diff --git a/icu4c/source/test/intltest/ustrtest.cpp b/icu4c/source/test/intltest/ustrtest.cpp
index 522a0473ec..5490e21653 100644
--- a/icu4c/source/test/intltest/ustrtest.cpp
+++ b/icu4c/source/test/intltest/ustrtest.cpp
@@ -82,10 +82,10 @@ UnicodeStringTest::TestBasicManipulation()
     if (test2 != expectedValue)
         errln("operator+=() failed:  expected \"" + expectedValue + "\"\n,got \"" + test2 + "\"");
     
-    if (test1.size() != 70)
-        errln("size() failed: expected 70, got " + test1.size());
-    if (test2.size() != 30)
-        errln("size() failed: expected 30, got " + test2.size());
+    if (test1.length() != 70)
+        errln("length() failed: expected 70, got " + test1.length());
+    if (test2.length() != 30)
+        errln("length() failed: expected 30, got " + test2.length());
 }
 
 void
@@ -225,7 +225,7 @@ UnicodeStringTest::TestRemoveReplace()
               "  expected \"The SPAM in SPAM SPAM SPAM on the SPAM\",\n"
               "  got \"" + test1 + "\"");
 
-    for (UTextOffset i = 0; i < test1.size(); i++)
+    for (UTextOffset i = 0; i < test1.length(); i++)
         if (test5[i] != 'S' && test5[i] != 'P' && test5[i] != 'A' && test5[i] != 'M' && test5[i] != ' ')
             test1[i] = 'x';
 
@@ -235,7 +235,7 @@ UnicodeStringTest::TestRemoveReplace()
               "  got \"" + test1 + "\"");
 
     test1.remove();
-    if (test1.size() != 0)
+    if (test1.length() != 0)
         errln("Remove() failed: expected empty string, got \"" + test1 + "\"");
 }
 
@@ -301,14 +301,14 @@ UnicodeStringTest::TestCaseConversion()
     if (test3 != expectedResult)
         errln("toUpper failed: expected \"" + expectedResult + "\", got \"" + test3 + "\".");
     
-    test4.replace(0, test4.size(), uppercaseGreek);
+    test4.replace(0, test4.length(), uppercaseGreek);
 
     test4.toLower(Locale("el", "GR"));
     expectedResult = lowercaseGreek;
     if (test4 != expectedResult)
         errln("toLower failed: expected \"" + expectedResult + "\", got \"" + test4 + "\".");
     
-    test4.replace(0, test4.size(), lowercaseGreek);
+    test4.replace(0, test4.length(), lowercaseGreek);
 
     test4.toUpper();
     expectedResult = uppercaseGreek;
@@ -326,14 +326,14 @@ UnicodeStringTest::TestSearching()
     uint16_t occurrences = 0;
     UTextOffset startPos = 0;
     for ( ;
-          startPos != -1 && startPos < test1.size();
+          startPos != -1 && startPos < test1.length();
           (startPos = test1.indexOf(test2, startPos)) != -1 ? (++occurrences, startPos += 4) : 0)
         ;
     if (occurrences != 6)
         errln("indexOf failed: expected to find 6 occurrences, found " + occurrences);
 
     for ( occurrences = 0, startPos = 10;
-          startPos != -1 && startPos < test1.size();
+          startPos != -1 && startPos < test1.length();
           (startPos = test1.indexOf(test2, startPos)) != -1 ? (++occurrences, startPos += 4) : 0)
         ;
     if (occurrences != 4)
@@ -341,28 +341,28 @@ UnicodeStringTest::TestSearching()
 
     UTextOffset endPos = 28;
     for ( occurrences = 0, startPos = 5;
-          startPos != -1 && startPos < test1.size();
+          startPos != -1 && startPos < test1.length();
           (startPos = test1.indexOf(test2, startPos, endPos - startPos)) != -1 ? (++occurrences, startPos += 4) : 0)
         ;
     if (occurrences != 4)
         errln("indexOf with starting and ending offsets failed: expected to find 4 occurrences, found " + occurrences);
 
     for ( occurrences = 0, startPos = 0;
-          startPos != -1 && startPos < test1.size();
+          startPos != -1 && startPos < test1.length();
           (startPos = test1.indexOf(testChar, startPos)) != -1 ? (++occurrences, startPos += 1) : 0)
         ;
     if (occurrences != 16)
         errln("indexOf with character failed: expected to find 16 occurrences, found " + occurrences);
 
     for ( occurrences = 0, startPos = 10;
-          startPos != -1 && startPos < test1.size();
+          startPos != -1 && startPos < test1.length();
           (startPos = test1.indexOf(testChar, startPos)) != -1 ? (++occurrences, startPos += 1) : 0)
         ;
     if (occurrences != 12)
         errln("indexOf with character & start offset failed: expected to find 12 occurrences, found " + occurrences);
 
     for ( occurrences = 0, startPos = 5, endPos = 28;
-          startPos != -1 && startPos < test1.size();
+          startPos != -1 && startPos < test1.length();
           (startPos = test1.indexOf(testChar, startPos, endPos - startPos)) != -1 ? (++occurrences, startPos += 1) : 0)
         ;
     if (occurrences != 10)
@@ -553,16 +553,16 @@ UnicodeStringTest::TestMiscellaneous()
         errln("getUChars() affected the string!");
 
     UTextOffset i;
-    for (i = 0; i < test2.size(); i++)
+    for (i = 0; i < test2.length(); i++)
         if (test2[i] != test4[i])
             errln(UnicodeString("getUChars() failed: strings differ at position ") + i);
 
     test4 = test1.orphanStorage();
 
-    if (test1.size() != 0)
+    if (test1.length() != 0)
         errln("orphanStorage() failed: orphaned string's contents is " + test1);
 
-    for (i = 0; i < test2.size(); i++)
+    for (i = 0; i < test2.length(); i++)
         if (test2[i] != test4[i])
             errln(UnicodeString("orphanStorage() failed: strings differ at position ") + i);