diff -r 9e9aa450a5f8 Lib/test/test_subprocess.py
--- a/Lib/test/test_subprocess.py	Sat Mar 05 20:29:01 2011 +0100
+++ b/Lib/test/test_subprocess.py	Sat Mar 05 16:47:07 2011 -0800
@@ -119,6 +119,24 @@
                              env=newenv)
         self.assertEqual(rc, 1)
 
+    def test_stdout_large(self):
+        # see: issue #11395
+        p = subprocess.Popen([sys.executable, "-c",
+                             "print(b'a' * 66000)"],
+                             stderr=subprocess.PIPE)
+        self.addCleanup(p.stderr.close)
+        p.wait()
+        self.assertEqual(p.returncode, 0)
+
+    def test_stdout_binlarge(self):
+        # see: issue #11395
+        p = subprocess.Popen([sys.executable, "-u", "-c",
+                              "print(b'a' * 66000)"],
+                             stderr=subprocess.PIPE)
+        self.addCleanup(p.stderr.close)
+        p.wait()
+        self.assertEqual(p.returncode, 0)
+
     def test_stdin_none(self):
         # .stdin is None when not redirected
         p = subprocess.Popen([sys.executable, "-c", 'print("banana")'],
diff -r 9e9aa450a5f8 Modules/_io/fileio.c
--- a/Modules/_io/fileio.c	Sat Mar 05 20:29:01 2011 +0100
+++ b/Modules/_io/fileio.c	Sat Mar 05 16:47:07 2011 -0800
@@ -650,7 +650,7 @@
 fileio_write(fileio *self, PyObject *args)
 {
     Py_buffer pbuf;
-    Py_ssize_t n;
+    Py_ssize_t n, len;
 
     if (self->fd < 0)
         return err_closed();
@@ -663,7 +663,17 @@
     if (_PyVerify_fd(self->fd)) {
         Py_BEGIN_ALLOW_THREADS
         errno = 0;
-        n = write(self->fd, pbuf.buf, pbuf.len);
+        len = pbuf.len;
+#if defined(MS_WIN64) || defined(MS_WINDOWS)
+        /* See: issue #11395 */
+        if (len > 32000 && isatty(self->fd))
+            len = 32000;
+        if (len > INT_MAX)
+            len = INT_MAX;
+        n = write(self->fd, pbuf.buf, (int)len);
+#else
+        n = write(self->fd, pbuf.buf, len);
+#endif
         Py_END_ALLOW_THREADS
     } else
         n = -1;