diff -r 5c09e1c57200 Lib/xmlrpc/client.py
--- a/Lib/xmlrpc/client.py	Wed Mar 20 20:16:47 2013 +0100
+++ b/Lib/xmlrpc/client.py	Wed Mar 20 18:27:44 2013 -0700
@@ -682,9 +682,16 @@
         try:
             f = self.dispatch[tag]
         except KeyError:
-            pass # unknown tag ?
+            pass  # unknown tag ?
         else:
-            return f(self, "".join(self._data))
+            # Avoid a data copy if only one item
+            if len(self._data) != 1:
+                data = ''.join(self._data)
+            else:
+                data = self._data[0]
+            # Free _data as soon as we can, to avoid keeping memory too long
+            self._data = []
+            return f(self, data)
 
     #
     # accelerator support