diff --git a/intl/lwbrk/src/nsLWBreakerFImp.h b/intl/lwbrk/src/nsLWBreakerFImp.h
index 7baeb87a45b..53682fdbee3 100644
--- a/intl/lwbrk/src/nsLWBreakerFImp.h
+++ b/intl/lwbrk/src/nsLWBreakerFImp.h
@@ -40,7 +40,7 @@
 
 
 
-#include "nsCom.h"
+#include "nscore.h"
 #include "nsISupports.h"
 
 #include "nsILineBreakerFactory.h"
diff --git a/intl/unicharutil/src/nsCaseConversionImp2.h b/intl/unicharutil/src/nsCaseConversionImp2.h
index 66b27aa4da8..1189010d4c0 100644
--- a/intl/unicharutil/src/nsCaseConversionImp2.h
+++ b/intl/unicharutil/src/nsCaseConversionImp2.h
@@ -39,7 +39,7 @@
 #ifndef nsCaseConversionImp2_h__
 #define nsCaseConversionImp2_h__
 
-#include "nsCom.h"
+#include "nscore.h"
 #include "nsISupports.h"
 
 #include "nsICaseConversion.h"
diff --git a/intl/unicharutil/src/nsCategoryImp.cpp b/intl/unicharutil/src/nsCategoryImp.cpp
index 7a44639fec9..b99eeb0c8e4 100644
--- a/intl/unicharutil/src/nsCategoryImp.cpp
+++ b/intl/unicharutil/src/nsCategoryImp.cpp
@@ -36,7 +36,7 @@
  *
  * ***** END LICENSE BLOCK ***** */
 
-#include "nsCom.h"
+#include "nscore.h"
 #include "pratom.h"
 #include "nsUUDll.h"
 #include "nsISupports.h"
diff --git a/intl/unicharutil/src/nsCategoryImp.h b/intl/unicharutil/src/nsCategoryImp.h
index a4aaf6488e7..0edad6dd73c 100644
--- a/intl/unicharutil/src/nsCategoryImp.h
+++ b/intl/unicharutil/src/nsCategoryImp.h
@@ -38,7 +38,7 @@
 #ifndef nsCategoryImp_h__
 #define nsCategoryImp_h__
 
-#include "nsCom.h"
+#include "nscore.h"
 #include "nsISupports.h"
 #include "nsIUGenCategory.h"
 
diff --git a/intl/unicharutil/src/nsUnicodeNormalizer.h b/intl/unicharutil/src/nsUnicodeNormalizer.h
index a92783222c7..242f26e8e93 100644
--- a/intl/unicharutil/src/nsUnicodeNormalizer.h
+++ b/intl/unicharutil/src/nsUnicodeNormalizer.h
@@ -38,7 +38,7 @@
 #ifndef nsUnicodeNormalizer_h__
 #define nsUnicodeNormalizer_h__
 
-#include "nsCom.h"
+#include "nscore.h"
 #include "nsISupports.h"
 
 #include "nsIUnicodeNormalizer.h"
diff --git a/mailnews/base/src/nsMessenger.h b/mailnews/base/src/nsMessenger.h
index 8d4bf806a1b..b89921f5725 100644
--- a/mailnews/base/src/nsMessenger.h
+++ b/mailnews/base/src/nsMessenger.h
@@ -38,7 +38,6 @@
 #ifndef __nsMsgAppCore_h
 #define __nsMsgAppCore_h
 
-#include "nsCom.h"
 #include "nscore.h"
 #include "nsIMessenger.h"
 #include "nsCOMPtr.h"
diff --git a/mailnews/base/util/nsMsgIncomingServer.cpp b/mailnews/base/util/nsMsgIncomingServer.cpp
index cc786d51521..45416517de5 100644
--- a/mailnews/base/util/nsMsgIncomingServer.cpp
+++ b/mailnews/base/util/nsMsgIncomingServer.cpp
@@ -38,7 +38,6 @@
 
 #include "nsMsgIncomingServer.h"
 #include "nscore.h"
-#include "nsCom.h"
 #include "plstr.h"
 #include "prmem.h"
 #include "prprf.h"
diff --git a/modules/oji/src/nsJVMManager.h b/modules/oji/src/nsJVMManager.h
index b30b82d1856..24c24fb860b 100644
--- a/modules/oji/src/nsJVMManager.h
+++ b/modules/oji/src/nsJVMManager.h
@@ -40,7 +40,7 @@
 
 #include "jvmmgr.h"
 #include "prtypes.h"
-#include "nsCom.h"
+#include "nscore.h"
 #include "jni.h"
 #include "jsdbgapi.h"
 #include "nsError.h"
diff --git a/uriloader/base/nsDocLoader.cpp b/uriloader/base/nsDocLoader.cpp
index b23c9730e35..20ea848c25d 100644
--- a/uriloader/base/nsDocLoader.cpp
+++ b/uriloader/base/nsDocLoader.cpp
@@ -48,7 +48,7 @@
 
 #include "nsIURL.h"
 #include "nsCOMPtr.h"
-#include "nsCom.h"
+#include "nscore.h"
 #include "nsWeakPtr.h"
 
 #include "nsIDOMWindow.h"
diff --git a/uriloader/exthandler/mac/nsDecodeAppleFile.h b/uriloader/exthandler/mac/nsDecodeAppleFile.h
index ca030186432..0c2ad18bcb3 100644
--- a/uriloader/exthandler/mac/nsDecodeAppleFile.h
+++ b/uriloader/exthandler/mac/nsDecodeAppleFile.h
@@ -38,7 +38,6 @@
 #ifndef nsDecodeAppleFile_h__
 #define nsDecodeAppleFile_h__
 
-#include "nsCom.h"
 #include "nscore.h"
 #include "nsCOMPtr.h"
 #include "nsIFile.h"
diff --git a/xpcom/ds/nsFixedSizeAllocator.h b/xpcom/ds/nsFixedSizeAllocator.h
index 76c7324e354..507c191099a 100644
--- a/xpcom/ds/nsFixedSizeAllocator.h
+++ b/xpcom/ds/nsFixedSizeAllocator.h
@@ -129,7 +129,6 @@
 #define nsFixedSizeAllocator_h__
 
 #include "nscore.h"
-#include "nsCom.h"
 #include "nsError.h"
 #include "plarena.h"
 
diff --git a/xpcom/ds/nsHashtable.h b/xpcom/ds/nsHashtable.h
index 27353be386d..db627f4f037 100644
--- a/xpcom/ds/nsHashtable.h
+++ b/xpcom/ds/nsHashtable.h
@@ -40,7 +40,6 @@
 #include "pldhash.h"
 #include "prlock.h"
 #include "nscore.h"
-#include "nsCom.h"
 #include "nsString.h"
 
 class nsIObjectInputStream;
diff --git a/xpcom/ds/nsStatistics.h b/xpcom/ds/nsStatistics.h
index fe9e81dfbb4..e69de29bb2d 100644
--- a/xpcom/ds/nsStatistics.h
+++ b/xpcom/ds/nsStatistics.h
@@ -1,73 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/*
- * The contents of this file are subject to the Mozilla Public License
- * Version 1.1 (the "MPL"); you may not use this file except in
- * compliance with the MPL.  You may obtain a copy of the MPL at
- * http://www.mozilla.org/MPL/
- *
- * Software distributed under the MPL is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the MPL
- * for the specific language governing rights and limitations under the
- * MPL.
- *
- * The Initial Developer of this code under the MPL is Netscape
- * Communications Corporation.  Portions created by Netscape are
- * Copyright (C) 1999 Netscape Communications Corporation.  All Rights
- * Reserved.
- *
- * Original Author:
- *   Chris Waterson <waterson@netscape.com>
- */
-
-/*
-
-  An object that collects distribution data
-
-*/
-#ifndef nsStatistics_h__
-#define nsStatistics_h__
-
-#include <stdio.h>
-#include "nscore.h"
-#include "nsCom.h"
-#include "plhash.h"
-
-/**
- * An object that collects distribution data.
- */
-class NS_COM nsStatistics
-{
-public:
-    nsStatistics(const char* aTopic);
-    ~nsStatistics();
-
-    /**
-     * Add a value to the distribution
-     */
-    void Record(PRInt32 aValue);
-
-    /**
-     * Clear the information collected so far
-     */
-    void Clear();
-
-    /**
-     * Print the mean, standard deviation, and distribution
-     * of values reported so far
-     */
-    void Print(FILE* aStream);
-
-protected:
-    const char* mTopic;
-    PLHashTable* mDistribution;
-    PRInt32 mCount;
-    PRInt32 mMinimum;
-    PRInt32 mMaximum;
-    double mSum;
-    double mSumOfSquares;
-
-    static PLHashNumber PR_CALLBACK HashPRInt32(const void* aKey);
-};
-
-
-#endif
diff --git a/xpcom/ds/nsVector.h b/xpcom/ds/nsVector.h
index 2e5bd34814a..e69de29bb2d 100644
--- a/xpcom/ds/nsVector.h
+++ b/xpcom/ds/nsVector.h
@@ -1,93 +0,0 @@
-/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
-/* ***** BEGIN LICENSE BLOCK *****
- * Version: NPL 1.1/GPL 2.0/LGPL 2.1
- *
- * The contents of this file are subject to the Netscape Public License
- * Version 1.1 (the "License"); you may not use this file except in
- * compliance with the License. You may obtain a copy of the License at
- * http://www.mozilla.org/NPL/
- *
- * Software distributed under the License is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
- * for the specific language governing rights and limitations under the
- * License.
- *
- * The Original Code is mozilla.org code.
- *
- * The Initial Developer of the Original Code is 
- * Netscape Communications Corporation.
- * Portions created by the Initial Developer are Copyright (C) 1998
- * the Initial Developer. All Rights Reserved.
- *
- * Contributor(s):
- *
- * Alternatively, the contents of this file may be used under the terms of
- * either the GNU General Public License Version 2 or later (the "GPL"), or 
- * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
- * in which case the provisions of the GPL or the LGPL are applicable instead
- * of those above. If you wish to allow use of your version of this file only
- * under the terms of either the GPL or the LGPL, and not to allow others to
- * use your version of this file under the terms of the NPL, indicate your
- * decision by deleting the provisions above and replace them with the notice
- * and other provisions required by the GPL or the LGPL. If you do not delete
- * the provisions above, a recipient may use your version of this file under
- * the terms of any one of the NPL, the GPL or the LGPL.
- *
- * ***** END LICENSE BLOCK ***** */
-
-#ifndef nsVector_h__
-#define nsVector_h__
-
-#include "plvector.h"
-#include "nsCom.h"
-
-class nsVector : public PLVector {
-public:
-// Construction
-    nsVector(PRUint32 initialSize = 0, PRInt32 initialGrowBy = 0) {
-        PL_VectorInitialize(this, initialSize, initialGrowBy);
-    }
-    ~nsVector(void) { PL_VectorFinalize(this); }
-
-// Attributes
-    PRUint32 GetSize(void) const { return PL_VectorGetSize(this); }
-    PRUint32 GetUpperBound(void) const { return GetSize() - 1; }
-    PRBool SetSize(PRUint32 nNewSize, PRInt32 nGrowBy = PL_VECTOR_GROW_DEFAULT) {
-        return PL_VectorSetSize(this, nNewSize, nGrowBy);
-    }
-    PRBool IsValidIndex(PRUint32 indx) { return PL_VectorIsValidIndex(this, indx); }
-
-// Operations
-    // Clean up
-    void Compact(void) { PL_VectorCompact(this); }
-    void RemoveAll(void) { SetSize(0); }
-    void Copy(nsVector* src, PRUint32 len, PRUint32 dstPos = 0, PRUint32 srcPos = 0) {
-        PL_VectorCopy(this, dstPos, src, srcPos, len);
-    }
-
-    // Accessing elements
-    void* Get(PRUint32 indx) const { return PL_VectorGet(this, indx); }
-    void Set(PRUint32 indx, void* newElement) { PL_VectorSet(this, indx, newElement); }
-    void*& ElementAt(PRUint32 indx) { return *PL_VectorGetAddr(this, indx); }
-
-    // Potentially growing the array
-    PRInt32 Add(void* newElement) { return PL_VectorAdd(this, newElement); }
-
-    // overloaded operator helpers
-    void* operator[](PRUint32 indx) const { return Get(indx); }
-    void*& operator[](PRUint32 indx) { return ElementAt(indx); }
-
-    // Operations that move elements around
-    void Insert(PRUint32 indx, void* newElement, PRInt32 count = 1) {
-        PL_VectorInsert(this, indx, newElement, count);
-    }
-    void Remove(PRUint32 indx, PRInt32 count = 1) {
-        PL_VectorRemove(this, indx, count);
-    }
-
-#ifdef DEBUG
-    void AssertValid(void) const { PL_VectorAssertValid((PLVector*)this); }
-#endif
-};
-
-#endif
diff --git a/xpcom/glue/nsTraceRefcnt.h b/xpcom/glue/nsTraceRefcnt.h
index d332f5172d0..38d9863ff0d 100644
--- a/xpcom/glue/nsTraceRefcnt.h
+++ b/xpcom/glue/nsTraceRefcnt.h
@@ -38,9 +38,8 @@
 #ifndef nsTraceRefcnt_h___
 #define nsTraceRefcnt_h___
 
-#include "nsCom.h"
-
-#include <stdio.h>
+#include "nscore.h"
+#include <stdio.h> // XXXldb We should remove this and add it where needed.
 
 class nsISupports;
 
diff --git a/xpcom/tests/TestAutoPtr.cpp b/xpcom/tests/TestAutoPtr.cpp
index cf23de594fc..cff0f864883 100644
--- a/xpcom/tests/TestAutoPtr.cpp
+++ b/xpcom/tests/TestAutoPtr.cpp
@@ -23,7 +23,7 @@
 
 #include "nsAutoPtr.h"
 #include <stdio.h>
-#include "nsCom.h"
+#include "nscore.h"
 
 class TestObjectBaseA {
     public: