diff --git a/Doc/lib/libstdtypes.tex b/Doc/lib/libstdtypes.tex
index 2ba87c4..27f1c52 100644
--- a/Doc/lib/libstdtypes.tex
+++ b/Doc/lib/libstdtypes.tex
@@ -1154,9 +1154,8 @@
 \begin{methoddesc}[file]{truncate}{\optional{size}}
   Truncate the file's size.  If the optional \var{size} argument
   present, the file is truncated to (at most) that size.  The size
-  defaults to the current position.  Availability of this function
-  depends on the operating system version (for example, not all
-  \UNIX{} versions support this operation).
+  defaults to the current position.
+  Availability:  Windows, many \UNIX variants.
 \end{methoddesc}
 
 \begin{methoddesc}[file]{write}{str}
diff --git a/Lib/test/test_largefile.py b/Lib/test/test_largefile.py
index abfee39..bc24635 100644
--- a/Lib/test/test_largefile.py
+++ b/Lib/test/test_largefile.py
@@ -128,20 +128,29 @@
 expect(f.read(1), 'a') # the 'a' that was written at the end of the file above
 f.close()
 
-
-# XXX add tests for truncate if it exists
-# XXX has truncate ever worked on Windows? specifically on WinNT I get:
-#     "IOError: [Errno 13] Permission denied"
-##try:
-##      newsize = size - 10
-##      f.seek(newsize)
-##      f.truncate()
-##      expect(f.tell(), newsize)
-##      newsize = newsize - 1
-##      f.seek(0)
-##      f.truncate(newsize)
-##      expect(f.tell(), newsize)
-##except AttributeError:
-##      pass
+if hasattr(f, 'truncate'):
+    if test_support.verbose:
+        print 'try truncate'
+    f = open(name, 'r+b')
+    f.seek(0, 2)
+    expect(f.tell(), size+1)
+    # Cut it back via seek + truncate with no argument.
+    newsize = size - 10
+    f.seek(newsize)
+    f.truncate()
+    expect(f.tell(), newsize)
+    # Ensure that truncate(bigger than true size) doesn't grow the file.
+    f.truncate(size)
+    expect(f.tell(), newsize)
+    # Ensure that truncate(smaller than true size) shrinks the file.
+    newsize -= 1
+    f.seek(0)
+    f.truncate(newsize)
+    expect(f.tell(), newsize)
+    # cut it waaaaay back
+    f.truncate(1)
+    f.seek(0)
+    expect(len(f.read()), 1)
+    f.close()
 
 os.unlink(name)
diff --git a/Misc/NEWS b/Misc/NEWS
index 58d5a66..6611c5d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -73,7 +73,7 @@
 - Because Python's magic number scheme broke on January 1st, we decided
   to stop Python development.  Thanks for all the fish!
 
-- Some of us don't like fish, so we changed Python's magic number 
+- Some of us don't like fish, so we changed Python's magic number
   scheme to a new one. See Python/import.c for details.
 
 New platforms
@@ -84,6 +84,10 @@
 
 Windows
 
+- file.truncate([newsize]) now works on Windows for all newsize values.
+  It used to fail if newsize didn't fit in 32 bits, reflecting a
+  limitation of MS _chsize (which is no longer used).
+
 - os.waitpid() is now implemented for Windows, and can be used to block
   until a specified process exits.  This is similar to, but not exactly
   the same as, os.waitpid() on POSIX systems.  If you're waiting for
diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index d6b2229..f2f5dcf 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -10,8 +10,10 @@
 
 #ifdef MS_WIN32
 #define fileno _fileno
-/* can (almost fully) duplicate with _chsize, see file_truncate */
+/* can simulate truncate with Win32 API functions; see file_truncate */
 #define HAVE_FTRUNCATE
+#define WINDOWS_LEAN_AND_MEAN
+#include <windows.h>
 #endif
 
 #ifdef macintosh
@@ -379,6 +381,9 @@
 	newsizeobj = NULL;
 	if (!PyArg_ParseTuple(args, "|O:truncate", &newsizeobj))
 		return NULL;
+
+	/* Set newsize to current postion if newsizeobj NULL, else to the
+	   specified value. */
 	if (newsizeobj != NULL) {
 #if !defined(HAVE_LARGEFILE_SUPPORT)
 		newsize = PyInt_AsLong(newsizeobj);
@@ -389,37 +394,67 @@
 #endif
 		if (PyErr_Occurred())
 			return NULL;
-	} else {
-		/* Default to current position*/
+	}
+	else {
+		/* Default to current position. */
 		Py_BEGIN_ALLOW_THREADS
 		errno = 0;
 		newsize = _portable_ftell(f->f_fp);
 		Py_END_ALLOW_THREADS
-		if (newsize == -1) {
-		        PyErr_SetFromErrno(PyExc_IOError);
-			clearerr(f->f_fp);
-			return NULL;
-		}
+		if (newsize == -1)
+			goto onioerror;
 	}
+
+	/* Flush the file. */
 	Py_BEGIN_ALLOW_THREADS
 	errno = 0;
 	ret = fflush(f->f_fp);
 	Py_END_ALLOW_THREADS
-	if (ret != 0) goto onioerror;
+	if (ret != 0)
+		goto onioerror;
 
 #ifdef MS_WIN32
-	/* can use _chsize; if, however, the newsize overflows 32-bits then
-	   _chsize is *not* adequate; in this case, an OverflowError is raised */
-	if (newsize > LONG_MAX) {
-		PyErr_SetString(PyExc_OverflowError,
-			"the new size is too long for _chsize (it is limited to 32-bit values)");
-		return NULL;
-	} else {
-		Py_BEGIN_ALLOW_THREADS
+	/* MS _chsize doesn't work if newsize doesn't fit in 32 bits,
+	   so don't even try using it.  truncate() should never grow the
+	   file, but MS SetEndOfFile will grow a file, so we need to
+	   compare the specified newsize to the actual size.  Some
+	   optimization could be done here when newsizeobj is NULL. */
+	{
+		Py_off_t currentEOF;	/* actual size */
+		HANDLE hFile;
+		int error;
+
+		/* First move to EOF, and set currentEOF to the size. */
 		errno = 0;
-		ret = _chsize(fileno(f->f_fp), (long)newsize);
-		Py_END_ALLOW_THREADS
-		if (ret != 0) goto onioerror;
+		if (_portable_fseek(f->f_fp, 0, SEEK_END) != 0)
+			goto onioerror;
+		errno = 0;
+		currentEOF = _portable_ftell(f->f_fp);
+		if (currentEOF == -1)
+			goto onioerror;
+
+		if (newsize > currentEOF)
+			newsize = currentEOF;	/* never grow the file */
+
+		/* Move to newsize, and truncate the file there. */
+		if (newsize != currentEOF) {
+			errno = 0;
+			if (_portable_fseek(f->f_fp, newsize, SEEK_SET) != 0)
+				goto onioerror;
+			Py_BEGIN_ALLOW_THREADS
+			errno = 0;
+			hFile = (HANDLE)_get_osfhandle(fileno(f->f_fp));
+			error = hFile == (HANDLE)-1;
+			if (!error) {
+				error = SetEndOfFile(hFile) == 0;
+				if (error)
+					errno = EACCES;
+			}
+			Py_END_ALLOW_THREADS
+			if (error)
+				goto onioerror;
+		}
+
 	}
 #else
 	Py_BEGIN_ALLOW_THREADS