This is a package of commutative diagram macros built on top of Xy-pic by Michael Barr (email: firstname.lastname@example.org). Its use is unrestricted. It may be freely distributed, unchanged, for non-commercial or commercial use. If changed, it must be renamed. Inclusion in a commercial software package is also permitted, but I would appreciate receiving a free copy for my personal examination and use. There are no guarantees that this package is good for anything. I have tested it with LaTeX 2e, LaTeX 2.09 and Plain TeX. Although I know of no reason it will not work with AMSTeX, I have not tested it.