diff -r e97639fc4cd1 Doc/library/threading.rst
--- a/Doc/library/threading.rst	Thu Jun 11 19:51:17 2009 +0200
+++ b/Doc/library/threading.rst	Thu Jun 11 22:36:32 2009 +0000
@@ -26,6 +26,12 @@
    Starting with Python 2.5, several Thread methods raise :exc:`RuntimeError`
    instead of :exc:`AssertionError` if called erroneously.
 
+.. note::
+
+   Due to the GIL, in CPython only one thread can execute Python code 
+   at once. Thus threads do not really run concurrently, not even on 
+   muli-core computers. For making your application scalable on 
+   multi-core machines, you are advised to use :mod:`multiprocessing`.
 
 This module defines the following functions and objects: