Hi Ed, I wrote the SPIDER volume file reader for Chimera. You can get it from http://www.cgl.ucsf.edu/home/goddard/spidervol.tar.gz and unpack it % cd /usr/local/chimera/share % tar zxf spidervol.tar.gz It includes a new VolumeData/fileformats.py that adds the SPIDER file reader to the list of supported file formats, and a VolumeData/spider directory that contains the Python code to read the data. I don't think this should be announced on the SPIDER newsgroup until we make our next Chimera release that includes it. I'd like to figure out how the spacing between grid points in physical units is handled by SPIDER. I see a "scale" parameter in the SPIDER file header, but the documentation says SPIDER does not use this, and in the file you sent me it was set to zero. Chimera likes to know the correct scale in physical units (eg angstroms or nanometers) so when a second model is opened they are drawn to the same scale. There are entry fields to hand set the scale in the Volume Viewer dialog, but it is nicer to be able to extract this from the file header. Tom