When I start up Chimera from the command line under Leopard, I get a lot of messages such as: The process has forked and you cannot use this CoreFoundation functionality safely. You MUST exec(). Break on __THE_PROCESS_HAS_FORKED_AND_YOU_CANNOT_USE_THIS_COREFOUNDATION_FUNCTIONALITY___YOU_MUST_EXEC__ () to debug. Chimera still runs, but I thought this is probably something to be dealt with sooner than later. I did some digging and came across the following technical note from Apple: http://developer.apple.com/technotes/tn2005/tn2083.html The reference to the fork message is at the bottom of the page. I also found on another site the following advice for an X11 application: "I've updated the OSX Readme TclTk build example to include an extra configure option: --disable-corefoundation Since the example is for an X11 TclTk build, CoreFoundation isn't really necessary, so this is OK." Because Chimera uses Tk, I thought this might be something to try to avoid these error messages and possible instability down the line. Bernard Heymann Rm 1515, 50 South Dr, NIH, Bethesda, 20892-8025 Tel 301-451-8241, Fax 301-480-7629