Cate, Here are a few mmCIF tutorials I "allthewebbed" recently (I just happened to learn how google keeps tabs on you, which piqued my libertarian sensibilities): http://www.sdsc.edu/pb/cif/tutorial_mm.html http://ndbserver.rutgers.edu/NDB/SEATTLE/mmcif- tutorial/ciftutorial.html The second link is really nice. Btw, you might want to share your ideas on how to incorporate support for mmCIF into our code base, given that there's CIFLIB already. Regards, Serge Need a new email address that people can remember Check out the new EudoraMail at http://www.eudoramail.com