diff --git a/icu4c/source/i18n/ucol.cpp b/icu4c/source/i18n/ucol.cpp
index 5f46d9302d..0f5882daab 100644
--- a/icu4c/source/i18n/ucol.cpp
+++ b/icu4c/source/i18n/ucol.cpp
@@ -3670,7 +3670,6 @@ inline uint8_t *packFrench(uint8_t *primaries, uint8_t *primEnd, uint8_t *second
   uint8_t secondary;
   int32_t count2 = 0;
   uint32_t i = 0, size = 0;
-  uint8_t *primStart = primaries;
   // we use i here since the key size already accounts for terminators, so we'll discard the increment
   addWithIncrement(primaries, primEnd, i, UCOL_LEVELTERMINATOR); 
   /* If there are any unresolved continuation secondaries, reverse them here so that we can reverse the whole secondary thing */
diff --git a/icu4c/source/i18n/ucol_bld.cpp b/icu4c/source/i18n/ucol_bld.cpp
index 1eb7e4cde1..b33c1e4486 100644
--- a/icu4c/source/i18n/ucol_bld.cpp
+++ b/icu4c/source/i18n/ucol_bld.cpp
@@ -915,7 +915,6 @@ ucol_uprv_bld_copyRangeFromUCA(UColTokenParser *src, tempUCATable *t,
                                UErrorCode *status) {
   //UChar decomp[256];
   uint32_t CE = UCOL_NOT_FOUND;
-  uint32_t tag = UCOL_NOT_FOUND;
   UChar32 u = 0;
   UCAElements el;
   el.isThai = FALSE;
@@ -1072,8 +1071,6 @@ UCATableHeader *ucol_assembleTailoringTable(UColTokenParser *src, UErrorCode *st
     }
   }
 
-  uint32_t CE = UCOL_NOT_FOUND;
-  UChar u = 0;
   UCAElements el;
   el.isThai = FALSE;
   el.prefixSize = 0;
diff --git a/icu4c/source/test/cintltst/capitst.c b/icu4c/source/test/cintltst/capitst.c
index ca1d5f14a0..7c6fb05762 100644
--- a/icu4c/source/test/cintltst/capitst.c
+++ b/icu4c/source/test/cintltst/capitst.c
@@ -1505,8 +1505,8 @@ static void TestAttribute()
 
 void TestGetTailoredSet() {
   struct {
-    char *rules;
-    char *tests[20];
+    const char *rules;
+    const char *tests[20];
     int32_t testsize;
   } setTest[] = {
     { "&a < \\u212b", { "\\u212b", "A\\u030a", "\\u00c5" }, 3},
diff --git a/icu4c/source/test/cintltst/cloctst.c b/icu4c/source/test/cintltst/cloctst.c
index 920e7aaee5..aa4378270d 100644
--- a/icu4c/source/test/cintltst/cloctst.c
+++ b/icu4c/source/test/cintltst/cloctst.c
@@ -23,6 +23,7 @@
 #include "unicode/ustring.h"
 #include "cintltst.h"
 #include "ccolltst.h"
+#include "cstring.h"
 
 #include "unicode/ures.h"
 #ifdef WIN32
diff --git a/icu4c/source/test/cintltst/cnormtst.c b/icu4c/source/test/cintltst/cnormtst.c
index 46d4d2b4ab..a182e31387 100644
--- a/icu4c/source/test/cintltst/cnormtst.c
+++ b/icu4c/source/test/cintltst/cnormtst.c
@@ -101,6 +101,8 @@ const static char* compatTests[][3] = {
     
 };
 
+void addNormTest(TestNode** root);
+
 void addNormTest(TestNode** root)
 {
     addTest(root, &TestAPI, "tscoll/cnormtst/TestAPI");
diff --git a/icu4c/source/test/cintltst/usettest.c b/icu4c/source/test/cintltst/usettest.c
index c37b8e0435..15cb214a11 100644
--- a/icu4c/source/test/cintltst/usettest.c
+++ b/icu4c/source/test/cintltst/usettest.c
@@ -44,7 +44,6 @@ addUSetTest(TestNode** root) {
 static void Testj2269() {
   UErrorCode status = U_ZERO_ERROR;
   UChar a[4] = { 0x61, 0x62, 0x63, 0 };
-  UChar b[4] = { 0x61, 0x62, 0x63, 0 };
   USet *s = uset_open(1, 0);
   uset_addString(s, a, 3);
   a[0] = 0x63; a[1] = 0x63;
diff --git a/icu4c/source/tools/genrb/derb.c b/icu4c/source/tools/genrb/derb.c
index 3161756071..ba5bd20879 100644
--- a/icu4c/source/tools/genrb/derb.c
+++ b/icu4c/source/tools/genrb/derb.c
@@ -698,7 +698,6 @@ static void printOutBundle(FILE *out, UConverter *converter, UResourceBundle *re
                   }
               }
             } else { /* we have to use low level access to do this */
-              uint16_t i = 0;
               Resource r = RES_BOGUS;
               for(i = 0; i < ures_getSize(resource); i++) {
                 /* need to know if it's an alias */
diff --git a/icu4c/source/tools/genrb/parse.c b/icu4c/source/tools/genrb/parse.c
index e35d087f1e..fc203c956c 100644
--- a/icu4c/source/tools/genrb/parse.c
+++ b/icu4c/source/tools/genrb/parse.c
@@ -1225,13 +1225,8 @@ parseInclude(char *tag, uint32_t startline, UErrorCode *status)
     char             *filename;
     uint32_t          line;
     UChar *pTarget     = NULL;
-    UChar *target      = NULL;
-    UChar *targetLimit = NULL;
 
     UCHARBUF *ucbuf;
-    UChar32   c     = 0;
-    uint32_t  size = 0;
-    UBool quoted = FALSE;
     char     *fullname = NULL;
     int32_t  count     = 0;
     const char* cp = NULL;
diff --git a/icu4c/source/tools/genrb/rle.c b/icu4c/source/tools/genrb/rle.c
index 42cfaec55b..6a6a5b612c 100644
--- a/icu4c/source/tools/genrb/rle.c
+++ b/icu4c/source/tools/genrb/rle.c
@@ -104,7 +104,6 @@ encodeRunByte(uint16_t* buffer,uint16_t* bufLimit, uint8_t value, int32_t length
  */
 static int32_t 
 encodeRunShort(uint16_t* buffer,uint16_t* bufLimit, uint16_t value, int32_t length,UErrorCode* status) {
-    uint16_t* saveBuf =  buffer;
     int32_t num=0;
     if (length < 4) {
         int j=0;
@@ -147,7 +146,6 @@ encodeRunShort(uint16_t* buffer,uint16_t* bufLimit, uint16_t value, int32_t leng
  */
 int32_t 
 usArrayToRLEString(const uint16_t* src,int32_t srcLen,uint16_t* buffer, int32_t bufLen,UErrorCode* status) {
-    const uint16_t* saveBuf = buffer;
     uint16_t* bufLimit =  buffer+bufLen;
     int32_t num = 0;
     if(buffer < bufLimit){
diff --git a/icu4c/source/tools/genrb/wrtxml.c b/icu4c/source/tools/genrb/wrtxml.c
index aadc974a28..2773fa99a6 100644
--- a/icu4c/source/tools/genrb/wrtxml.c
+++ b/icu4c/source/tools/genrb/wrtxml.c
@@ -101,7 +101,6 @@ static char* convertAndEscape(char** pDest, int32_t destCap, int32_t* destLength
 	int32_t i=0;
 	char* dest=NULL;
 	char* temp=NULL;
-	int32_t len=0;
 	int32_t destLen=0;
 	
 	if(status==NULL || U_FAILURE(*status) || pDest==NULL  || srcLen==0 || src == NULL){
@@ -383,7 +382,7 @@ bin_write_xml( struct SResource *res, UErrorCode *status) {
                                                     (res->u.fBinaryValue.fFileName !=NULL ? 
 													uprv_strlen(res->u.fBinaryValue.fFileName) :0)));
     char* buffer = NULL;
-    char* ext = NULL;
+    const char* ext = NULL;
     fn[0]=0;
 
     if(res->u.fBinaryValue.fLength>100){
@@ -454,7 +453,6 @@ bin_write_xml( struct SResource *res, UErrorCode *status) {
 }
 
 
-static UBool start = TRUE;
 
 static void 
 table_write_xml(struct SResource *res, UErrorCode *status) {
diff --git a/icu4c/source/tools/toolutil/ucbuf.h b/icu4c/source/tools/toolutil/ucbuf.h
index 7ce57b2fa7..e8d5a768ca 100644
--- a/icu4c/source/tools/toolutil/ucbuf.h
+++ b/icu4c/source/tools/toolutil/ucbuf.h
@@ -162,7 +162,8 @@ ucbuf_ungetc(int32_t ungetChar,UCHARBUF* buf);
  * @return The input FileStream if its charset was autodetected; NULL otherwise.
  */
 U_CAPI FileStream * U_EXPORT2
-ucbuf_autodetect(const char* fileName, const char** cp,UConverter** conv, int32_t* signatureLength,UErrorCode* error);
+ucbuf_autodetect(const char* fileName, const char** cp,UConverter** conv,
+int32_t* signatureLength, UErrorCode* status);
 
 /**
  * Autodetects the encoding of the file stream. Only Unicode charsets are autodectected. 
@@ -181,7 +182,7 @@ ucbuf_autodetect(const char* fileName, const char** cp,UConverter** conv, int32_
  */
 
 U_CAPI UBool U_EXPORT2
-ucbuf_autodetect_fs(FileStream* in, const char** cp, UConverter** conv, int32_t* signatureLength, UErrorCode* error);
+ucbuf_autodetect_fs(FileStream* in, const char** cp, UConverter** conv, int32_t* signatureLength, UErrorCode* status);
 
 /**
  * Returns the approximate size in UChars required for converting the file to UChars
diff --git a/icu4c/source/tools/toolutil/uperf.cpp b/icu4c/source/tools/toolutil/uperf.cpp
index 6d3f186fa0..7ee2c27cc1 100644
--- a/icu4c/source/tools/toolutil/uperf.cpp
+++ b/icu4c/source/tools/toolutil/uperf.cpp
@@ -361,9 +361,9 @@ UBool UPerfTest::runTestLoop( char* testname, char* par )
                   }
 */
                   if(events == -1){
-                      fprintf(stdout,"= %s end: %f loops: %i operations: %i \n",name , t , loops, testFunction->getOperationsPerIteration());
+                      fprintf(stdout,"= %s end: %f loops: %i operations: %li \n",name , t , loops, testFunction->getOperationsPerIteration());
                   }else{
-                      fprintf(stdout,"= %s end: %f loops: %i operations: %i events: %i\n",name , t , loops, testFunction->getOperationsPerIteration(), events);
+                      fprintf(stdout,"= %s end: %f loops: %i operations: %li events: %li\n",name , t , loops, testFunction->getOperationsPerIteration(), events);
                   }
               }else{
 /*
@@ -374,9 +374,9 @@ UBool UPerfTest::runTestLoop( char* testname, char* par )
                   }                   
 */
                   if(events == -1){
-                      fprintf(stdout,"= %s end %f %i %i\n",name , t , loops, testFunction->getOperationsPerIteration());
+                      fprintf(stdout,"= %s end %f %i %li\n",name , t , loops, testFunction->getOperationsPerIteration());
                   }else{
-                      fprintf(stdout,"= %s end %f %i %i %i\n",name , t , loops, testFunction->getOperationsPerIteration(), events);
+                      fprintf(stdout,"= %s end %f %i %li %li\n",name , t , loops, testFunction->getOperationsPerIteration(), events);
                   }
               }
             }
diff --git a/icu4c/source/tools/toolutil/utimer.h b/icu4c/source/tools/toolutil/utimer.h
index bdbe07a3b4..a7f9c63d8f 100644
--- a/icu4c/source/tools/toolutil/utimer.h
+++ b/icu4c/source/tools/toolutil/utimer.h
@@ -183,7 +183,7 @@ typedef void FuntionToBeTimed(void* param);
         struct timeval placeHolder;
     };
     
-    int32_t uprv_initFrequency(UTimer* timer)
+    int32_t uprv_initFrequency(UTimer* /*timer*/)
     {
         return 0;
     }
@@ -198,7 +198,7 @@ typedef void FuntionToBeTimed(void* param);
         t2 =  (double)timer2->start.tv_sec + (double)timer2->start.tv_usec/(1000*1000);
         return (t2-t1);
     }
-    UBool uprv_compareFrequency(UTimer* timer1, UTimer* timer2){
+    UBool uprv_compareFrequency(UTimer* /*timer1*/, UTimer* /*timer2*/){
         return TRUE;
     }