We reviewed rigorous evaluations of programs to enhance the quality and economy of primary care. We identified 36 evaluations published from 1980 through 1992. We abstracted data on objectives, setting(s), patients and processes, outcomes, and costs of care. We identified successful programs, as well as significant gaps in our knowledge of how to improve aspects of care. In specific, computer reminders and social influence-based methods fostered preventive and economic care. Nurse implementation of prevention protocols increased their performance. Multidisciplinary teams improved access and economy. Regional organization of practices or telephone management improved access; regionalization also reduced emergency care. Improvements were not found in continuity, comprehensiveness, humanistic process, physical environment, or health outcomes. Primary care practices can implement several programs to continuously improve prevention and access, and to reduce costs and use of unnecessary services. Research documenting how to accomplish other major goals, including health outcome changes, in different practice types is needed.