Hello, I posted the new version of the proposed Boost Exception library last Friday, you can get the new documentation and code here: http://www.revergestudios.com/boost-exception/boost-exception.htm. I have received two suggestions by email to remove the use of macros for type registration. Currently, to register tag_foo with the exception library, and to specify that its value is of type int, you'd use: BOOST_REGISTER_EXCEPTION_INFO(tag_foo,int) One suggestion was to use this instead: struct tag_foo { typedef int value_type; }; Another suggestion was very similar, with the following syntax: struct tag_foo: exception_info_tag<int> { }; I encourage everyone to provide your feedback in the mailing list instead of by email, so we can have an open discussion. Thanks, Emil Dotchevski