diff -r aaa68dce117e Doc/library/stdtypes.rst
--- a/Doc/library/stdtypes.rst	Thu Aug 09 21:38:23 2012 +0200
+++ b/Doc/library/stdtypes.rst	Fri Aug 10 19:33:04 2012 +0300
@@ -2105,8 +2105,10 @@
 
    .. method:: pop()
 
-      Remove and return an arbitrary element from the set.  Raises
-      :exc:`KeyError` if the set is empty.
+      Remove and return an arbitrary element from the set.
+      Note that the element is *not* selected randomly,
+      the exact algorithm is implementation-specific.
+      Raises :exc:`KeyError` if the set is empty.
 
    .. method:: clear()
 
diff -r aaa68dce117e Objects/setobject.c
--- a/Objects/setobject.c	Thu Aug 09 21:38:23 2012 +0200
+++ b/Objects/setobject.c	Fri Aug 10 19:33:04 2012 +0300
@@ -743,6 +743,8 @@
 }
 
 PyDoc_STRVAR(pop_doc, "Remove and return an arbitrary set element.\n\
+Note that the element is not selected randomly,\n\
+the exact algorithm is implementation-specific.\n\
 Raises KeyError if the set is empty.");
 
 static int