The Residents' Computer Bulletin Board System (RBBS) originated as an offshoot of a research project designed at a 1988 meeting of Baltimore's chief medical residents. Beginning on March 1, 1989, RBBS offered electronic mail, bulletins, file transfers, newsletters, and data collections to physicians-in-training. It operated for 695 days before ResNet, sponsored by the American College of Physicians, superseded it. This report details how medical students, residents, and fellows used this electronic means of communication and offers some conclusions about the elements that future computerized bulletin board systems should have to succeed.