Hi, The build flags for HP-UX are set to "<threading>multi" and "64-bit" in RC_1_34_0/tools/build/v2/tools/acc.jam i.e. "-mt" and "+DD64". 1.actions acc.link bind NEEDLIBS 2.actions acc.link.dll bind NEEDLIBS 3.actions acc.compile.c 4.actions acc.compile.c++ Has this been done on purpose ? Regards, Prashant Thakre