Some additional information pertaining to BOOST_NO_INTRINSIC_WCHAR_T using the Intel C++ 7.1 compiler in my MSVC 6 SP6 environment: Using Boost v1.31.0 + STLport v5.0-125 + Intel C++ v7.1 (I updated to build 20030910Z) inside of MSVC 6 SP6 with a fairly recent MS Platform SDK, I simply could not get boost/config/compiler/intel.hpp to send me down the road to glory. Inside of config/compiler/intel.hpp, _WCHAR_T_DEFINED is defined resulting in BOOST_NO_INTRINSIC_WCHAR_T not being set. Subsequently, this results in the compile-time error: boost/type_traits/is_integral.hpp(38): error: class "boost::is_integral<unsigned short>" has already been defined Per "Compiler errors with Intel 7.1 and type_traits" (http://lists.boost.org/MailArchives/boost/msg53033.php), specifically John Maddock's reply (http://lists.boost.org/MailArchives/boost/msg53121.php), I short-circuited the logic in config/compiler/intel.hpp and explicitly defined BOOST_NO_INTRINSIC_WCHAR_T in config/user.hpp. This seems to work acceptably for this project. But I'm not at all comfortable with this solution because I really don't understand what the fundamental issue is with all this wchar_t stuff. Forgive my ignorance but if, with my current working config, if I declare a wchar_t type in my code I will get a 16-bit UCS-2 character. Correct? Having now poured over all postings related to this subject in the archive, I have an inkling that the root of all this stems from the way the compiler handles type aliasing? That is, with BOOST_NO_INTRINSIC_WCHAR_T a defined a wchar_t is actually an alias for an unsigned int whereas in the case !defined(BOOST_NO_INTRINSIC_WCHAR_T), the compiler treats wchar_t as an intrinsic type? And from this we get these template specialization errors? Or am I way off? - Regards Chris