diff --git a/js/src/jsopcode.c b/js/src/jsopcode.c
index 98ade32488eb..3271901be44c 100644
--- a/js/src/jsopcode.c
+++ b/js/src/jsopcode.c
@@ -660,7 +660,7 @@ Decompile(SprintStack *ss, jsbytecode *pc, intN nb)
     JSOp op, lastop, saveop;
     JSCodeSpec *cs, *topcs;
     jssrcnote *sn;
-    const char *lval, *rval, *xval;
+    const char *lval, *rval=NULL, *xval;
     jsint i, argc;
     char **argv;
     JSAtom *atom;
diff --git a/js/src/jsxdrapi.c b/js/src/jsxdrapi.c
index f238da13cc4a..51cdda22b070 100644
--- a/js/src/jsxdrapi.c
+++ b/js/src/jsxdrapi.c
@@ -265,7 +265,7 @@ JS_XDRUint16(JSXDRState *xdr, uint16 *s)
 JS_PUBLIC_API(JSBool)
 JS_XDRUint32(JSXDRState *xdr, uint32 *lp)
 {
-    JSBool ok;
+    JSBool ok = JS_FALSE;
     if (xdr->mode == JSXDR_ENCODE) {
 	uint32 xl = JSXDR_SWAB32(*lp);
 	ok = xdr->ops->set32(xdr, &xl);
diff --git a/js/src/liveconnect/jsj_JavaArray.c b/js/src/liveconnect/jsj_JavaArray.c
index 91024e60dd4f..1133cae897f5 100644
--- a/js/src/liveconnect/jsj_JavaArray.c
+++ b/js/src/liveconnect/jsj_JavaArray.c
@@ -52,7 +52,7 @@ try_convert_to_jsint(JSContext *cx, jsval idval)
     if (JS7_ISDEC(*cp)) {
         jsuint index = JS7_UNDEC(*cp++);
         jsuint oldIndex = 0;
-        jsuint c;
+        jsuint c = 0;
         if (index != 0) {
             while (JS7_ISDEC(*cp)) {
                 oldIndex = index;
diff --git a/modules/libpref/src/prefapi.c b/modules/libpref/src/prefapi.c
index 3b2db16215c1..415d11816388 100644
--- a/modules/libpref/src/prefapi.c
+++ b/modules/libpref/src/prefapi.c
@@ -1108,7 +1108,7 @@ PREF_GetColorPrefDWord(const char *pref_name, uint32 *colorref)
 {
 	char colstr[8];
 	int iSize = 8;
-	uint8 red, green, blue;
+	uint8 red=0, green=0, blue=0;
 
 	int result = PREF_GetCharPref(pref_name, colstr, &iSize);
 	
@@ -1283,7 +1283,7 @@ PREF_GetDefaultColorPrefDWord(const char *pref_name, uint32 * colorref)
 {
 	char colstr[8];
 	int iSize = 8;
-	uint8 red, green, blue;
+	uint8 red=0, green=0, blue=0;
 
 	int result = PREF_GetDefaultCharPref(pref_name, colstr, &iSize);
 	
@@ -2092,7 +2092,7 @@ JSBool PR_CALLBACK pref_NativeGetLDAPAttr
 PR_IMPLEMENT(int)
 pref_printDebugInfo(PRHashEntry *he, int i, void *arg)
 {
-	char *buf1, *buf2;
+	char *buf1=NULL, *buf2=NULL;
 	PrefValue val;
 	PrefChildIter* pcs = (PrefChildIter*) arg;
 	PrefNode *pref = (PrefNode *) he->value;
diff --git a/modules/libpref/src/prefapi.cpp b/modules/libpref/src/prefapi.cpp
index 3b2db16215c1..415d11816388 100644
--- a/modules/libpref/src/prefapi.cpp
+++ b/modules/libpref/src/prefapi.cpp
@@ -1108,7 +1108,7 @@ PREF_GetColorPrefDWord(const char *pref_name, uint32 *colorref)
 {
 	char colstr[8];
 	int iSize = 8;
-	uint8 red, green, blue;
+	uint8 red=0, green=0, blue=0;
 
 	int result = PREF_GetCharPref(pref_name, colstr, &iSize);
 	
@@ -1283,7 +1283,7 @@ PREF_GetDefaultColorPrefDWord(const char *pref_name, uint32 * colorref)
 {
 	char colstr[8];
 	int iSize = 8;
-	uint8 red, green, blue;
+	uint8 red=0, green=0, blue=0;
 
 	int result = PREF_GetDefaultCharPref(pref_name, colstr, &iSize);
 	
@@ -2092,7 +2092,7 @@ JSBool PR_CALLBACK pref_NativeGetLDAPAttr
 PR_IMPLEMENT(int)
 pref_printDebugInfo(PRHashEntry *he, int i, void *arg)
 {
-	char *buf1, *buf2;
+	char *buf1=NULL, *buf2=NULL;
 	PrefValue val;
 	PrefChildIter* pcs = (PrefChildIter*) arg;
 	PrefNode *pref = (PrefNode *) he->value;