Ambulatory medical clinics at academic centers are reputed to be expensive, inefficient, and poorly regarded by the medical residents who staff them. In an effort to address these problems, some centers have reorganized their traditional clinics into group practices. These group practices are thought to be more effective for teaching and providing services than are the traditional clinics. This is a report on the results of a study in which the authors reorganized two of four firm clinics into group practices in order to test the influence of the organizational changes on the various aspects of ambulatory care. During this controlled prospective trial of the group practice model, higher show rates were observed for patients in the group practices than in the traditional clinics (70% vs 65%,P< 0.0005). The possible reasons for the higher rates are discussed.