Index: lib2to3/fixes/fix_imports.py
===================================================================
--- lib2to3/fixes/fix_imports.py	(revision 68503)
+++ lib2to3/fixes/fix_imports.py	(working copy)
@@ -72,9 +72,9 @@
               ( any | import_as_name< any 'as' any > |
                 import_as_names< any* >)  [')'] >
           """ % mod_list
-    yield """import_name< 'import' (dotted_as_name< (%s) 'as' any > |
+    yield """import_name< 'import' (dotted_as_name< (%s) 'as' as_what=any > |
                multiple_imports=dotted_as_names<
-                 any* dotted_as_name< (%s) 'as' any > any* >) >
+                 any* dotted_as_name< (%s) 'as' as_what=any > any* >) >
           """ % (mod_list, mod_list)
 
     # Find usages of module members in code e.g. thread.foo(bar)
@@ -117,6 +117,7 @@
     def start_tree(self, tree, filename):
         super(FixImports, self).start_tree(tree, filename)
         self.replace = {}
+        self.seen_cstringio = False
 
     def transform(self, node, results):
         import_mod = results.get("module_name")
@@ -127,7 +128,12 @@
             if "name_import" in results:
                 # If it's not a "from x import x, y" or "import x as y" import,
                 # marked its usage to be replaced.
-                self.replace[mod_name] = new_name
+                if not (mod_name == "StringIO" and self.seen_cstringio):
+                    self.replace[mod_name] = new_name
+            elif not self.seen_cstringio and mod_name == "cStringIO":
+                as_what = results.get("as_what")
+                if as_what is not None and as_what.value == "StringIO":
+                    self.seen_cstringio = True
             if "multiple_imports" in results:
                 # This is a nasty hack to fix multiple imports on a
                 # line (e.g., "import StringIO, urlparse"). The problem is that I