RasMol Version 2.6.4 is a minor update of the RasMol molecuar graphics package. This update includes mainly minor bug fixes and portability enhancements. I'm not actively working on improving RasMol, alas the commercial exploitation of RasMol provides little motivation for me to work on major enhancements for the public domain. Fortunately, RasMol already provides most of the functionality required by its 100,000+ users. However over the last few years I have made a significant number of small changes to the version I use internally. As these fix a number of portability problems that are becoming more widespread, I thought it was time to release this internal version and prevent "bit rot". Questions are best sent to the rasmol mailing list organized by Eric Martz (and his group) at the University of Massachusetts at Amherst. They have a RasMol WWW page at http://www.umass.edu/microbio/rasmol/