Brian, thanks for your answer! I removed and completely reinstalled the Developer Tools. The issue with gcc seems to be resolved now. My python binary is indeed the one of python.org, but nevertheless I also reinstalled Python 2.5. To install numpy I started all over again with svn. The results are, however, exactly the same. Then I tried a version lower: numpy-1.0.1 (instead of 1.0.2 of the trunk). The same error messages during the setup.py procedure, but they don't seem to matter this time: afterwards I can import numpy without any obvious problems. I know that numpy 1.0.2 installs well on my Linux box, but there I use gcc-3.4. instead of gcc-4.0. Might this be a compiler issue? What version of numpy did you install, did you notice any warning or error messages at all? Joris Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm