Hi, In my current project boost::regex was used previously from version v3 (boost 1.30.2) and there was no problem. Because I use a third party SDK that contains boost 1.33.1 I want to use boost and regex (v4) from this SDK. In the project there is a source file that includes "boost/regex.hpp". In the release version the file compiles, but in the debug version I get a lot of errors like: char_regex_traits.hpp(34) : error C2976: 'boost::regex_traits' : too few template arguments /basic_regex.hpp(186) : error C2825: 'traits': must be a class or namespace when followed by '::' basic_regex.hpp(186) : error C2039: 'size_type' : is not a member of '`global namespace'' I have now removed the preprocessor definition '_DEBUG' from the VC8 project that contains the source file but this makes no difference. Is there any idea what's going on here ? Wolfgang