The quality and cost of medical care provided by specially trained nurses in an internal medicine clinic was evaluated prospectively during a three-month period. Clinic physicians referred patients to these nurses when they believed that the nurse could contribute to the patient's overall health care. Nurse care was judged to be adequate in dealing with 98% of old problems (defined by the physician) and 85% of new problems (detected by nurse). Scheduled visits to the physician and unscheduled visits decreased significantly (P less than .05) during the period of nurse care vs a control period, but the overall cost of health care per patient was increased significantly during the nurse care period (P less than .01) because of a disproportionate increase in visits to the nurse. We conclude that nurse care was feasible and of adequate quality. However, it was not cost-effective.