diff --git a/content/xul/templates/src/nsXULContentBuilder.cpp b/content/xul/templates/src/nsXULContentBuilder.cpp
index 91dfea86656..707c96ff83a 100644
--- a/content/xul/templates/src/nsXULContentBuilder.cpp
+++ b/content/xul/templates/src/nsXULContentBuilder.cpp
@@ -60,7 +60,6 @@
 #include "nsXULContentUtils.h"
 #include "nsXULElement.h"
 #include "nsXULTemplateBuilder.h"
-#include "nsSupportsArray.h"
 #include "nsNodeInfoManager.h"
 #include "nsContentCreatorFunctions.h"
 #include "nsContentUtils.h"
diff --git a/docshell/shistory/src/nsSHEntry.h b/docshell/shistory/src/nsSHEntry.h
index 0b5a1551827..a966b97e8f2 100644
--- a/docshell/shistory/src/nsSHEntry.h
+++ b/docshell/shistory/src/nsSHEntry.h
@@ -56,7 +56,7 @@
 #include "nsIEnumerator.h"
 #include "nsIHistoryEntry.h"
 #include "nsRect.h"
-#include "nsSupportsArray.h"
+#include "nsISupportsArray.h"
 #include "nsIMutationObserver.h"
 #include "nsExpirationTracker.h"
 #include "nsDocShellEditorData.h"
diff --git a/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp b/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp
index 19625b0af0b..85a576dbf17 100644
--- a/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp
+++ b/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp
@@ -1860,21 +1860,20 @@ void nsWebBrowserPersist::CleanupLocalFiles()
                 // recursed through to ensure they are actually empty.
 
                 PRBool isEmptyDirectory = PR_TRUE;
-                nsSupportsArray dirStack;
-                PRUint32 stackSize = 0;
+                nsCOMArray<nsISimpleEnumerator> dirStack;
+                PRInt32 stackSize = 0;
 
                 // Push the top level enum onto the stack
                 nsCOMPtr<nsISimpleEnumerator> pos;
                 if (NS_SUCCEEDED(file->GetDirectoryEntries(getter_AddRefs(pos))))
-                    dirStack.AppendElement(pos);
+                    dirStack.AppendObject(pos);
 
-                while (isEmptyDirectory &&
-                    NS_SUCCEEDED(dirStack.Count(&stackSize)) && stackSize > 0)
+                while (isEmptyDirectory && (stackSize = dirStack.Count()))
                 {
                     // Pop the last element
                     nsCOMPtr<nsISimpleEnumerator> curPos;
-                    dirStack.GetElementAt(stackSize - 1, getter_AddRefs(curPos));
-                    dirStack.RemoveElementAt(stackSize - 1);
+                    curPos = dirStack[stackSize-1];
+                    dirStack.RemoveObjectAt(stackSize - 1);
                     
                     // Test if the enumerator has any more files in it
                     PRBool hasMoreElements = PR_FALSE;
@@ -1908,9 +1907,9 @@ void nsWebBrowserPersist::CleanupLocalFiles()
                     // Push parent enumerator followed by child enumerator
                     nsCOMPtr<nsISimpleEnumerator> childPos;
                     childAsFile->GetDirectoryEntries(getter_AddRefs(childPos));
-                    dirStack.AppendElement(curPos);
+                    dirStack.AppendObject(curPos);
                     if (childPos)
-                        dirStack.AppendElement(childPos);
+                        dirStack.AppendObject(childPos);
 
                 }
                 dirStack.Clear();
diff --git a/js/src/xpconnect/src/xpcprivate.h b/js/src/xpconnect/src/xpcprivate.h
index 15549b5bddc..42daba04aaa 100644
--- a/js/src/xpconnect/src/xpcprivate.h
+++ b/js/src/xpconnect/src/xpcprivate.h
@@ -108,7 +108,7 @@
 #include "nsVariant.h"
 #include "nsIPropertyBag.h"
 #include "nsIProperty.h"
-#include "nsSupportsArray.h"
+#include "nsCOMArray.h"
 #include "nsTArray.h"
 #include "nsBaseHashtable.h"
 #include "nsHashKeys.h"
@@ -2738,9 +2738,8 @@ public:
     JSBool AppendElement(nsISupports* element);
 
 private:
-    nsSupportsArray mArray;
-    PRUint32        mIndex;
-    PRUint32        mCount;
+    nsCOMArray<nsISupports> mArray;
+    PRInt32                 mIndex;
 };
 
 /***************************************************************************/
diff --git a/js/src/xpconnect/src/xpcwrappedjsclass.cpp b/js/src/xpconnect/src/xpcwrappedjsclass.cpp
index 11c315f5b21..36c0efdd05e 100644
--- a/js/src/xpconnect/src/xpcwrappedjsclass.cpp
+++ b/js/src/xpconnect/src/xpcwrappedjsclass.cpp
@@ -490,36 +490,36 @@ NS_IMETHODIMP xpcProperty::GetValue(nsIVariant * *aValue)
 NS_IMPL_ISUPPORTS1(xpcPropertyBagEnumerator, nsISimpleEnumerator)
 
 xpcPropertyBagEnumerator::xpcPropertyBagEnumerator(PRUint32 count)
-    : mIndex(0), mCount(0)
+    : mIndex(0)
 {
-    mArray.SizeTo(count);
+    mArray.SetCapacity(count);
 }
 
 JSBool xpcPropertyBagEnumerator::AppendElement(nsISupports* element)
 {
-    if(!mArray.AppendElement(element))
+    if(!mArray.AppendObject(element))
         return JS_FALSE;
-    mCount++;
     return JS_TRUE;
 }
 
 /* boolean hasMoreElements (); */
 NS_IMETHODIMP xpcPropertyBagEnumerator::HasMoreElements(PRBool *_retval)
 {
-    *_retval = mIndex < mCount;
+    *_retval = mIndex < mArray.Count();
     return NS_OK;
 }
 
 /* nsISupports getNext (); */
 NS_IMETHODIMP xpcPropertyBagEnumerator::GetNext(nsISupports **_retval)
 {
-    if(!(mIndex < mCount))
+    if(!(mIndex < mArray.Count()))
     {
         NS_ERROR("Bad nsISimpleEnumerator caller!");
         return NS_ERROR_FAILURE;    
     }
     
-    *_retval = mArray.ElementAt(mIndex++);
+    *_retval = mArray.ObjectAt(mIndex++);
+    NS_IF_ADDREF(*_retval);
     return *_retval ? NS_OK : NS_ERROR_FAILURE;
 }
 
diff --git a/netwerk/base/src/nsIOService.h b/netwerk/base/src/nsIOService.h
index 719e643d144..400b4d8792b 100644
--- a/netwerk/base/src/nsIOService.h
+++ b/netwerk/base/src/nsIOService.h
@@ -50,7 +50,6 @@
 #include "nsURLHelper.h"
 #include "nsWeakPtr.h"
 #include "nsIURLParser.h"
-#include "nsSupportsArray.h"
 #include "nsIObserver.h"
 #include "nsWeakReference.h"
 #include "nsINetUtil.h"
diff --git a/netwerk/test/TestPageLoad.cpp b/netwerk/test/TestPageLoad.cpp
index eb89a5cde4e..11905788951 100644
--- a/netwerk/test/TestPageLoad.cpp
+++ b/netwerk/test/TestPageLoad.cpp
@@ -47,7 +47,7 @@
 #include "nsISupportsPrimitives.h"
 #include "prlong.h"
 #include "plstr.h"
-#include "nsSupportsArray.h"
+#include "nsCOMArray.h"
 #include "nsIComponentRegistrar.h"
 
 namespace TestPageLoad {
@@ -68,7 +68,7 @@ nsresult auxLoad(char *uriBuf);
 static nsCString globalStream;
 //static char urlBuf[256];
 static nsCOMPtr<nsIURI> baseURI;
-static nsCOMPtr<nsISupportsArray> uriList;
+static nsCOMArray<nsIURI> uriList;
 
 //Temp, should remove:
 static int numStart=0;
@@ -317,20 +317,16 @@ nsresult auxLoad(char *uriBuf)
     }
 
     //Compare to see if exists
-    PRUint32 num;
-    uriList->Count(&num);
     PRBool equal;
-    nsCOMPtr<nsIURI> uriTmp;
-    for(PRUint32 i = 0; i < num; i++) {
-      uriList->GetElementAt(i, getter_AddRefs(uriTmp));
-      uri->Equals(uriTmp, &equal);
+    for(PRInt32 i = 0; i < uriList.Count(); i++) {
+      uri->Equals(uriList[i], &equal);
       if(equal) {
         printf("(duplicate, canceling) %s\n",uriBuf); 
         return NS_OK;
       }
     }
     printf("\n");
-    uriList->AppendElement(uri);
+    uriList.AppendObject(uri);
     rv = NS_NewChannel(getter_AddRefs(chan), uri, nsnull, nsnull, callbacks);
     RETURN_IF_FAILED(rv, "NS_NewChannel");
 
@@ -371,9 +367,6 @@ int main(int argc, char **argv)
 
         PRTime start, finish;
 
-        uriList = do_CreateInstance(NS_SUPPORTSARRAY_CONTRACTID, &rv);
-        RETURN_IF_FAILED(rv, "do_CreateInstance(NS_SUPPORTSARRAY_CONTRACTID)");
-
         printf("Loading necko ... \n");
         nsCOMPtr<nsIChannel> chan;
         nsCOMPtr<nsIStreamListener> listener = new MyListener();
diff --git a/widget/src/xpwidgets/nsPrintOptionsImpl.cpp b/widget/src/xpwidgets/nsPrintOptionsImpl.cpp
index 874c5e51169..728355c0c33 100644
--- a/widget/src/xpwidgets/nsPrintOptionsImpl.cpp
+++ b/widget/src/xpwidgets/nsPrintOptionsImpl.cpp
@@ -48,7 +48,7 @@
 #include "nsISupportsPrimitives.h"
 #include "nsIWindowWatcher.h"
 #include "nsIDOMWindowInternal.h"
-#include "nsSupportsArray.h"
+#include "nsISupportsArray.h"
 #include "prprf.h"
 
 // For Prefs
diff --git a/xpcom/base/nsConsoleService.cpp b/xpcom/base/nsConsoleService.cpp
index 82a4b12a91a..1bcc8039bf3 100644
--- a/xpcom/base/nsConsoleService.cpp
+++ b/xpcom/base/nsConsoleService.cpp
@@ -46,7 +46,7 @@
 #include "nsMemory.h"
 #include "nsIServiceManager.h"
 #include "nsIProxyObjectManager.h"
-#include "nsSupportsArray.h"
+#include "nsCOMArray.h"
 #include "nsThreadUtils.h"
 
 #include "nsConsoleService.h"
@@ -111,10 +111,11 @@ nsConsoleService::Init()
 
 static PRBool snapshot_enum_func(nsHashKey *key, void *data, void* closure)
 {
-    nsISupportsArray *array = (nsISupportsArray *)closure;
+    nsCOMArray<nsIConsoleListener> *array =
+      reinterpret_cast<nsCOMArray<nsIConsoleListener> *>(closure);
 
-    // Copy each element into the temporary nsSupportsArray...
-    array->AppendElement((nsISupports*)data);
+    // Copy each element into the temporary nsCOMArray...
+    array->AppendObject((nsIConsoleListener*)data);
     return PR_TRUE;
 }
 
@@ -125,7 +126,7 @@ nsConsoleService::LogMessage(nsIConsoleMessage *message)
     if (message == nsnull)
         return NS_ERROR_INVALID_ARG;
 
-    nsSupportsArray listenersSnapshot;
+    nsCOMArray<nsIConsoleListener> listenersSnapshot;
     nsIConsoleMessage *retiredMessage;
 
     NS_ADDREF(message); // early, in case it's same as replaced below.
@@ -167,12 +168,7 @@ nsConsoleService::LogMessage(nsIConsoleMessage *message)
      * when we only care about the recursive case.
      */
     nsCOMPtr<nsIConsoleListener> listener;
-    nsresult rv;
-    nsresult returned_rv;
-    PRUint32 snapshotCount;
-    rv = listenersSnapshot.Count(&snapshotCount);
-    if (NS_FAILED(rv))
-        return rv;
+    PRInt32 snapshotCount = listenersSnapshot.Count();
 
     {
         nsAutoLock lock(mLock);
@@ -181,14 +177,8 @@ nsConsoleService::LogMessage(nsIConsoleMessage *message)
         mListening = PR_TRUE;
     }
 
-    returned_rv = NS_OK;
-    for (PRUint32 i = 0; i < snapshotCount; i++) {
-        rv = listenersSnapshot.GetElementAt(i, getter_AddRefs(listener));
-        if (NS_FAILED(rv)) {
-            returned_rv = rv;
-            break; // fall thru to mListening restore code below.
-        }
-        listener->Observe(message);
+    for (PRInt32 i = 0; i < snapshotCount; i++) {
+        listenersSnapshot[i]->Observe(message);
     }
     
     {
@@ -196,7 +186,7 @@ nsConsoleService::LogMessage(nsIConsoleMessage *message)
         mListening = PR_FALSE;
     }
 
-    return returned_rv;
+    return NS_OK;
 }
 
 NS_IMETHODIMP
diff --git a/xpcom/reflect/xptinfo/src/xptiInterfaceInfoManager.cpp b/xpcom/reflect/xptinfo/src/xptiInterfaceInfoManager.cpp
index 90fb9a7defd..210cdcde54b 100644
--- a/xpcom/reflect/xptinfo/src/xptiInterfaceInfoManager.cpp
+++ b/xpcom/reflect/xptinfo/src/xptiInterfaceInfoManager.cpp
@@ -1973,49 +1973,48 @@ public:
 
     xptiAdditionalManagersEnumerator();
 
-    PRBool SizeTo(PRUint32 likelyCount) {return mArray.SizeTo(likelyCount);}
+    PRBool SizeTo(PRUint32 likelyCount) {return mArray.SetCapacity(likelyCount);}
     PRBool AppendElement(nsIInterfaceInfoManager* element);
 
 private:
     ~xptiAdditionalManagersEnumerator() {}
 
-    nsSupportsArray mArray;
-    PRUint32        mIndex;
-    PRUint32        mCount;
+    nsCOMArray<nsISupports> mArray;
+    PRInt32                 mIndex;
 };
 
 NS_IMPL_ISUPPORTS1(xptiAdditionalManagersEnumerator, nsISimpleEnumerator)
 
 xptiAdditionalManagersEnumerator::xptiAdditionalManagersEnumerator()
-    : mIndex(0), mCount(0)
+    : mIndex(0)
 {
 }
 
 PRBool xptiAdditionalManagersEnumerator::AppendElement(nsIInterfaceInfoManager* element)
 {
-    if(!mArray.AppendElement(static_cast<nsISupports*>(element)))
+    if(!mArray.AppendObject(element))
         return PR_FALSE;
-    mCount++;
     return PR_TRUE;
 }
 
 /* boolean hasMoreElements (); */
 NS_IMETHODIMP xptiAdditionalManagersEnumerator::HasMoreElements(PRBool *_retval)
 {
-    *_retval = mIndex < mCount;
+    *_retval = mIndex < mArray.Count();
     return NS_OK;
 }
 
 /* nsISupports getNext (); */
 NS_IMETHODIMP xptiAdditionalManagersEnumerator::GetNext(nsISupports **_retval)
 {
-    if(!(mIndex < mCount))
+    if(!(mIndex < mArray.Count()))
     {
         NS_ERROR("Bad nsISimpleEnumerator caller!");
         return NS_ERROR_FAILURE;    
     }
 
-    *_retval = mArray.ElementAt(mIndex++);
+    *_retval = mArray.ObjectAt(mIndex++);
+    NS_IF_ADDREF(*_retval);
     return *_retval ? NS_OK : NS_ERROR_FAILURE;
 }
 
@@ -2030,11 +2029,9 @@ NS_IMETHODIMP xptiInterfaceInfoManager::AddAdditionalManager(nsIInterfaceInfoMan
                     static_cast<nsISupports*>(manager);
     { // scoped lock...
         nsAutoLock lock(mAdditionalManagersLock);
-        PRInt32 index;
-        nsresult rv = mAdditionalManagers.GetIndexOf(ptrToAdd, &index);
-        if(NS_FAILED(rv) || -1 != index)
+        if(mAdditionalManagers.IndexOf(ptrToAdd) != -1)
             return NS_ERROR_FAILURE;
-        if(!mAdditionalManagers.AppendElement(ptrToAdd))
+        if(!mAdditionalManagers.AppendObject(ptrToAdd))
             return NS_ERROR_OUT_OF_MEMORY;
     }
     return NS_OK;
@@ -2049,7 +2046,7 @@ NS_IMETHODIMP xptiInterfaceInfoManager::RemoveAdditionalManager(nsIInterfaceInfo
                     static_cast<nsISupports*>(manager);
     { // scoped lock...
         nsAutoLock lock(mAdditionalManagersLock);
-        if(!mAdditionalManagers.RemoveElement(ptrToRemove))
+        if(!mAdditionalManagers.RemoveObject(ptrToRemove))
             return NS_ERROR_FAILURE;
     }
     return NS_OK;
@@ -2058,10 +2055,8 @@ NS_IMETHODIMP xptiInterfaceInfoManager::RemoveAdditionalManager(nsIInterfaceInfo
 /* PRBool hasAdditionalManagers (); */
 NS_IMETHODIMP xptiInterfaceInfoManager::HasAdditionalManagers(PRBool *_retval)
 {
-    PRUint32 count;
-    nsresult rv = mAdditionalManagers.Count(&count);
-    *_retval = count != 0;
-    return rv;
+    *_retval = mAdditionalManagers.Count() > 0;
+    return NS_OK;
 }
 
 /* nsISimpleEnumerator enumerateAdditionalManagers (); */
@@ -2069,10 +2064,7 @@ NS_IMETHODIMP xptiInterfaceInfoManager::EnumerateAdditionalManagers(nsISimpleEnu
 {
     nsAutoLock lock(mAdditionalManagersLock);
 
-    PRUint32 count;
-    nsresult rv = mAdditionalManagers.Count(&count);
-    if(NS_FAILED(rv))
-        return rv;
+    PRInt32 count = mAdditionalManagers.Count();
 
     nsCOMPtr<xptiAdditionalManagersEnumerator> enumerator = 
         new xptiAdditionalManagersEnumerator();
@@ -2081,10 +2073,9 @@ NS_IMETHODIMP xptiInterfaceInfoManager::EnumerateAdditionalManagers(nsISimpleEnu
 
     enumerator->SizeTo(count);
 
-    for(PRUint32 i = 0; i < count; /* i incremented in the loop body */)
+    for(PRInt32 i = 0; i < count; /* i incremented in the loop body */)
     {
-        nsCOMPtr<nsISupports> raw = 
-            dont_AddRef(mAdditionalManagers.ElementAt(i++));
+        nsCOMPtr<nsISupports> raw = mAdditionalManagers.ObjectAt(i++);
         if(!raw)
             return NS_ERROR_FAILURE;
         nsCOMPtr<nsIWeakReference> weakRef = do_QueryInterface(raw);
@@ -2100,8 +2091,7 @@ NS_IMETHODIMP xptiInterfaceInfoManager::EnumerateAdditionalManagers(nsISimpleEnu
             else
             {
                 // The manager is no more. Remove the element.
-                if(!mAdditionalManagers.RemoveElementAt(--i))
-                    return NS_ERROR_FAILURE;
+                mAdditionalManagers.RemoveObjectAt(--i);
                 count--;
             }
         }
diff --git a/xpcom/reflect/xptinfo/src/xptiprivate.h b/xpcom/reflect/xptinfo/src/xptiprivate.h
index de36d65c3aa..f11043a73b7 100644
--- a/xpcom/reflect/xptinfo/src/xptiprivate.h
+++ b/xpcom/reflect/xptinfo/src/xptiprivate.h
@@ -66,9 +66,8 @@
 #include "nsMemory.h"
 
 #include "nsISupportsArray.h"
-#include "nsSupportsArray.h"
+#include "nsCOMArray.h"
 #include "nsInt64.h"
-
 #include "nsQuickSort.h"
 
 #include "nsXPIDLString.h"
@@ -968,7 +967,7 @@ private:
     PRLock*                      mAutoRegLock;
     PRMonitor*                   mInfoMonitor;
     PRLock*                      mAdditionalManagersLock;
-    nsSupportsArray              mAdditionalManagers;
+    nsCOMArray<nsISupports>      mAdditionalManagers;
     nsCOMPtr<nsISupportsArray>   mSearchPath;
 };