Aha, you need to set FUSION_MAX_VECTOR_SIZE, as well. Must have overlooked that in the documentation. This works now: #define FUSION_MAX_VECTOR_SIZE 20 #define FUSION_MAX_MAP_SIZE 20 #include <string> #include <boost/static_assert.hpp> #include <boost/fusion/sequence.hpp> using namespace std; using namespace boost; // Address contact namespace address_fields { struct _address_1_; struct _address_2_; struct _city_; struct _state_; struct _zip_; struct _country_; struct _phone_1_; struct _phone_2_; struct _email_1_; struct _email_2_; struct _fax_; struct _other_; } typedef fusion::map< fusion::pair< address_fields::_address_1_, string > , fusion::pair< address_fields::_address_2_, string > , fusion::pair< address_fields::_city_ , string > , fusion::pair< address_fields::_state_ , string > , fusion::pair< address_fields::_zip_ , string > , fusion::pair< address_fields::_country_ , string > , fusion::pair< address_fields::_phone_1_ , string > , fusion::pair< address_fields::_phone_2_ , string > , fusion::pair< address_fields::_email_1_ , string > , fusion::pair< address_fields::_email_2_ , string > , fusion::pair< address_fields::_fax_ , string > , fusion::pair< address_fields::_other_ , string > > address_type; int _tmain(int argc, _TCHAR* argv[]) { return 0; } Cool. I can proceed coding now. Christian