Gennadi, Thanks for the suggestions. I had reduced the failing test to a single BOOST_MESSAGE() macro call to simplify the error output. (All of the regex stuff links fine with the DLL.) When I try linking my entire test file, *ALL* of the unresolved references involve test_tools::tt_detail::... It's as if just the test tool details weren't created. If I remove the test tools library reference from the Makefile, then I get undefined test tools references for *OTHER* than details. So, at least something in the library is being used by the linker--just not the stuff from the details. I have no idea why the detail references would have been dropped. I have tried rebuilding the entire Boost library with bjam -sTOOLS=mingw -sMINGW_IMPLEMENTATION_DIR=E:\MinGW stage (I may have mis-remembered the exact name for the implementation directory, but I got it right.) This time I captured the output. There were error message about the serialization library because of wide characters, but no complaints about any of the others. The rebuilt library gives the same errors. I would certainly like to use the Boost test library, but for the moment, I'm going to have to go back to implementing it myself. Merrill