The advent of physician assistants raises questions regarding their appropriate utilization and monitoring. To determine practice patterns of physician assistants in settings independent of training programs, we studied 14 primary care practices in the rural southeast. Detailed observations, including appropriateness of medical care, were made on 788 outpatient-provider encounters. Physician assistants handled minor medical problems well and 61% of the patients observed in these practices fitted this category. Three practice patterns were observed: all patients were seen by the assistant initially, followed by the physician; patients managed concurrently by physician and assistant were not preselected; and patients with specific problems were assigned to the assistant. Properly managed, each of these patterns yielded competent care. Using these observations, proposed models of management and audit are presented for each practice pattern.