Hello, I have had similar problems in OSX 10.5 where exceptions are not caught, but with a different project. We are using CMake. I'm not sure how familiar you are with CMake, but it is a build system that allows you to generate projects for "native" development tools. In OSX, you can create Xcode projects or makefiles. If I use Xcode to build the project, I cannot catch exceptions consistently. If I use makefiles, it works fine. You can see the discussion on the CMake list here: http://www.cmake.org/pipermail/cmake/2008-January/019091.html The compiler flags that are used are significantly different, so that seems like a likely problem. Unfortunately, I have not had time to finish tracking the issue down. I'm not really familiar with building boost so maybe this is obvious, but how are you building it? What compiler flags are you using? David Thulson