From: ThoML Date: 2008-03-04T04:34:56+09:00 Subject: Re: overwriting (for real) a class > MyClass.new.foo # I want a no method exception here You can remove methods (there is a private method Class#remove_method) or remove the constant MyClass[1] and then define it anew. What would be a sensible use case for this? Thomas. [1] Example: http://groups.google.com/group/ruby-talk-google/msg/0fc850e23243d830