Just glancing at the serialization documentation.... The (member) function templates for serialize or save & load include an argument for the version. Where does this number come from? I guess the core routines insert a zero for that argument, unless overridden by a BOOST_CLASS_VERSION statement with a new number for a particular type. A type can conditionally change how it serializes based on the given version number. The examples show how to conditionally work with older versions in a backwards compatible fashion. But how should a serialization routine act if the version number given is too high? There doesn't seem to be a special exception for it. (The "unsupported_version" exception refers to the edition of the core routines, not a specific type's serialization.) -- Daryle Walker Mac, Internet, and Video Game Junkie darylew AT hotmail DOT com