Hi Grant, Here's an update on Chimera on Tiger. Chimera 1.2105 and earlier versions won't start on Tiger (Mac OS 10.4) because Chimera includes jpeg and tiff dynamic libraries that conflict with new libraries in Tiger. Yesterday I removed those conflicting libraries from Chimera, and recompiled another module that needs them (called _imaging) to link statically. Then Chimera starts on Tiger. Unfortunately with that problem taken care of I found that Chimera crashes when displaying a molecule ribbon. The crash dump shows it is in the Tiger OpenGL driver. This is likely a driver bug that Apple will have to fix and that may take months. I also found that molecular surfaces disappear as soon as you rotate the models. That may be the same or another OpenGL driver bug. I have only tested on my Mac with Radeon 9800 Pro graphics. The bug may not happen with Nvidia graphics cards or other ATI cards. I will try to make a version of Chimera that will start on Tiger available later today or tomorrow so you can try it with your graphics card. I'll send email when it is available to try. Tom