diff -r 3c437e591499 Lib/xmlrpc/client.py
--- a/Lib/xmlrpc/client.py	Tue Mar 26 02:38:40 2013 +0200
+++ b/Lib/xmlrpc/client.py	Tue Mar 26 10:17:58 2013 +0100
@@ -682,9 +682,12 @@
         try:
             f = self.dispatch[tag]
         except KeyError:
-            pass # unknown tag ?
+            pass  # unknown tag ?
         else:
-            return f(self, "".join(self._data))
+            data = ''.join(self._data)
+            # Free _data as soon as we can, to avoid keeping memory too long
+            self._data = []
+            return f(self, data)
 
     #
     # accelerator support