Look at example code:

BOOST_STATIC_ASSERT((boost::is_base_of::value_type));

Should be: BOOST_STATIC_ASSERT((boost::is_base_of::value)); The code does then compile with gcc, but not with VC++ 7.1. I think the problem here is that at the point you instantiate CTest, CDerived is an incomplete type - the static assert then fails because the compiler can't tell whether CDerived has any bases or not. I'm not sure if this helps, but if the test were to be instantiated from one of CDerived's member functions, then CDerived would be complete at the point of instantiation and the problem would go away. As it stands though you've given the compiler a cyclic instantiation-dependency, which it's free to resolve any way it chooses. HTH, John.