A while ago I posted a problem to the list about issues I was having using the beta Visual Studio SP1, statically linking to boost::threads and compiling with /clr ( http://thread.gmane.org/gmane.comp.lib.boost.user/22464/focus=22617 ). SP1 has been recently released and the problem still exists. I resubmitted a bug report to Microsoft and they have marked the bug as [Won't Fix]. https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?Feedba... A workaround is to use the DLL version of boost::threads. This is not ideal, as I'd rather not have yet another DLL to cart around with my application. I'm guessing that supporting the /clr switch in boost isn't a high priority but it is the most straightforward way to integrate portable code ( communications, etc ) into a C# application. John