Our objective was to design and evaluate an instru ment to assess the performance of a clinic in the deliv ery of preventive health services to a general medical clinic population. The patients were identified prospec tively ; data were obtained retrospectively with review of the charts. The study was conducted in a primary care clinic staffed primarily by internal medicine residents in an urban academic medical center. Patients who were receiving continuity care in the clinic and who were scheduled for an appointment during the 4-week study period were eligible for inclusion. Patients were iden tified by the appointment schedule. Charts were re viewed for the delivery of preventive health services. Data were abstracted utilizing a standard instrument. We found that the rate at which services were provided varied considerably by service and over time. The tech niques used provided some insight into methods for the evaluation of the delivery of preventive services. It should be possible to assess a clinic's performance over a range of services over its entire population over time. An understanding of this more global performance may provide a better tool for managers and researchers ad dressing these issues. There may be legitimate reasons for services not being provided. These issues are com plex and require sensitive, detailed investigation.