Hi! I am trying to build a project here with Visual Studio 2008 for a 64 bit platform, but I get a lot errors like the following (building it 32 bit works fine) 1>boosttest.obj : error LNK2001: unresolved external symbol "private: class boost::basic_regex<char,struct boost::regex_traits<char,class boost::w32_regex_traits<char> > > & __cdecl boost::basic_regex<char,struct boost::regex_traits<char,class boost::w32_regex_traits<char> > >::do_assign(char const *,char const *,unsigned int)" (?do_assign@?$basic_regex@DU?$regex_traits@DV?$w32_regex_traits@D@boost@@@boost@@@boost@@AEAAAEAV12@PEBD0I@Z) Here is what I did to build the libs: bjam msvc architecture=x86 address-model=64 stage bjam msvc architecture=x86 address-model=64 install I tried various versions of the above lines, with other parameters, or written differently e.g. (--toolset=msvc) but the end result did not change. Then I added the c:\boost\include\... and c:\boost\lib dir to (Tools -> Options -> VC++ Directories -> Platform x64 Include and Library files) To simplify the problem I created a new project and created a new Configuration for x64 ----- #include "stdafx.h" #define BOOST_LIB_DIAGNOSTIC #include <boost/regex.hpp> #include <string> int main() { boost::regex pat( "bla" ); } ----- I can build above fine in 32 bit mode, using the same(!) lib folder. So I assume, the created libs are 32 bit. (Can I check that somehow?) Any ideas what I might do wrong? Or what I might do to find out where the problem lies? Thanks, Christoph