Hi Batsal, Are the SPIDER and BRIX maps in Chimera related by some permutation of the x, y, or z axes? If there are a different number of grid points reported by the Chimera volume viewer dialog along each axis then the permutation should be apparent. If the axes have the same number of grid points, you might want to do a test with a map having different numbers of grid points along each axis. What conversion program did you use. I think this is most likely a problem with that program. But it could be a Chimera problem. The SPIDER format includes phi, theta, and gamma header values that specify a rotation that the Chimera file reader ignores. Here is documentation on SPIDER file format http://www.wadsworth.org/spider_doc/spider/docs/image_doc.html and here is documentation on BRIX format http://www.uoxray.uoregon.edu/tnt/manual/node104.html Let me know what you find out. Tom