diff -r 0b600abb3074 Lib/idlelib/ReplaceDialog.py
--- a/Lib/idlelib/ReplaceDialog.py	Fri Oct 14 11:34:29 2011 -0500
+++ b/Lib/idlelib/ReplaceDialog.py	Fri Oct 14 13:52:15 2011 -0500
@@ -58,11 +58,22 @@
             self.do_replace()
             self.do_find(0)
 
+    def avoid_bogus_escape(self, chars):
+        # count number of trailing \'s
+        e = 0
+        while e < len(chars) and chars[-(e+1)] == '\\':
+            e += 1
+
+        if (e % 2): # bogus escape if odd number of trailing \'s
+            chars += '\\'
+
+        return chars
+    
     def replace_all(self, event=None):
         prog = self.engine.getprog()
         if not prog:
             return
-        repl = self.replvar.get()
+        repl = self.avoid_bogus_escape(self.replvar.get())
         text = self.text
         res = self.engine.search_text(text, prog)
         if not res:
@@ -138,7 +149,7 @@
         m = prog.match(chars, col)
         if not prog:
             return False
-        new = m.expand(self.replvar.get())
+        new = m.expand(self.avoid_bogus_escape(self.replvar.get()))
         text.mark_set("insert", first)
         text.undo_block_start()
         if m.group():