Hi, whiline runnin the asio tests (under cygwin gcc-4.3 Windows XP ) as follows bjam cxxflags="-D__USE_W32_SOCKETS -D_WIN32_WINNT=0x0501" I got a compile error ../../../boost/asio/detail/impl/win_iocp_io_service.ipp: In member function â?~void boost::asio::detail::win_iocp_io_service::do_add_timer_queue(boost::asio::detail::timer_queue_base&)â?T: ../../../boost/asio/detail/impl/win_iocp_io_service.ipp:461: error: no matching function for call to â?~boost::asio::detail::posix_thread::posix_thread(boost::asio::detail::win_iocp_io_service::timer_thread_function&, int)â?T ../../../boost/asio/detail/posix_thread.hpp:38: note: candidates are: boost::asio::detail::posix_thread::posix_thread(const boost::asio::detail::posix_thread&) I have changed the prototype as the one for win_thread and now all the tests are OK. posix_thread(Function f, unsigned int = 0); Best, Vicente