Frequently, one reads in the literature about “the” emergency room, as if all emergency rooms were similar and a single model would suffice to describe them all. In this interview-survey of 1,113 patients attending the emergency rooms of four hospitals in New York City, however, it was found that each emergency room served very different populations and played very different roles in the medical-care patterns of those patients. As a result of this study and of a review of the previous literature, the authors suggest that there are three major roles for emergency rooms: 1. trauma treatment centers; 2. physician-substitutes when a private practitioner or out-patient clinic are not available; and 3. “family physician” to the urban poor. These roles are not mutually exclusive and all can be present to some degree in any one emergency room.