Hi, Just a few words to mention that I've finally managed to build numpy with the mingw-w64 project (port of mingw to AMD 64 bits MS OS), and it almost run OK. By almost, I mean that numpy.test() finishes without crash, assuming a few unit tests are skipped (some long double problems). Not all unit tests pass, but almost all of them are easy to fix problems in numpy (except for the long double problem). The drawback is that you can't do that just by using the mingw-w64 binaries, you have to build your own toolchain because of some bugs/missing features in mingw-w64. I've put the gory details there: http://scipy.org/scipy/numpy/wiki/MicrosoftToolchainSupport Hopefully, this should make it easier to add fortran support with gfortran, opening the possibility to have both numpy and scipy buildable on windows x64 with free compilers, David