Multiprocessing module needs some patches to succesfully builing and running on NetBSD. I made this patch and test on NetBSD 5rc2 (upcoming release). 1. we need working socket module (Modules/socketmodule.c) 2. mremap under NetBSD has different semantics: (Modules/mmapmodule.c) 3. finally, we need settings for netbsd in setup.py: (setup.py) After patching and building: netbsd5# ./python -bb -E Lib/test/regrtest.py test_multiprocessing test_multiprocessing 1 test OK.