The original OrbPlot 1.0 was written by E. D. Glendening, J. E. Carpenter, and F. Weinhold (1985-1990). Contouring routines were written by D. P. Anderson and HP and Regis graphics PLOT10-emulation routines by John Carpenter, Mark Muyskens, and Scott Ostrander for the Chemistry Department system (used and distributed by permission). OrbPlot 2.0 incorporated revisions written by F. Weinhold (1992) and was distributed through TCI/NBO Software, UW-Madison, for VAX/Regis systems. Subsequently, X-Windows library calls were provided by Z. Havlas and MS-Windows calls by S. Wilkens for inclusion in the TCI/NBO distribution. We gratefully acknowledge these contributors and the helpful suggestions of many users.