The output from b2 is in the boost-build.log file. Note the fact that it's saying that "/permissive-" is an extra argument. I was trying to turn on MSVC's standards-conformance mode. How do I do this when building Boost using MSVC without getting this error? b2 doesn't like the dash [-] at the end of permissive [it assumes it's the begin of another flag]. I'm just making this up here, but try to double-quote it. ""/permissive-"", maybe that works, I don't know. If not, you should write to the developer-list: boost@lists.boost.org, as in that case, this needs a fix in the b2-code [as it seems you do it right], or maybe one of the resident gurus knows another way to get that to pass. degski -- *“If something cannot go on forever, it will stop" - Herbert Stein*