Hospital tumor conferences (tumor boards) were observed and evaluated over an 18-month period to determine their organizational and educational characteristics as well as their impact on conference participants. In conjunction with a previous nationwide survey of tumor conferences, this study was designed to identify features that would facilitate the learning that occurs in conference sessions. Study investigators observed a regional sample of 43 tumor boards in 37 participating hospitals, which included 513 sessions at general (hospital-wide) conferences and 198 sessions at specialty conferences. A total of 1,866 tumor cases were presented during these 711 conferences. Participants completed questionnaires to supplement the investigators' evaluations. Session observations revealed several ways in which tumor boards could increase their educational impact on participants, including combining case presentations with presentations of related didactic material and using the method of progressive disclosure to promote increased participation in discussions related to retrospective case presentations. Improvements can be made in session organization and case presentation with the potential for increasing participant learning with little increase in the effort or expense associated with tumor conferences.