This report describes the systematic use of emergency-room data to (1) define the experiences of a group of pediatric interns in their emergency-room rotation (especially as they relate to their role as future pediatric practitioners), (2) evaluate, supervise, and learn from their performance in this primary care setting, and (3) provide an ongoing weekly list of illnesses diagnosed in the emergency room as an epidemiological sentinel for the larger community. The future applications of this type of systematic approach, perhaps with computer technology, offer the opportunity for comparison of delivery, quality, and cost of health care between various sources of primary care (emergency-room facilities, private physicians' offices, neighborhood health centers, and health maintenance organizations.