National Institute of Mental Health regulations require each federally funded community mental health center assume responsibility for psychiatric care to inhabitants of a catchment area. The effect of catchmenting on clinical practice has not been previously examined in any detail. In this study services offered in an outpatient clinic, as part of a catchmented program, are compared to services offered in another outpatient clinic located in the same building, serving a similar population, staffed by comparable clinicians, but without catchmented responsibility. With catchmenting, intake was briefer, more patients started treatment, waiting lists were shorter, greater use was made of crisis-oriented approaches and medication, and there was less patient dissatisfaction. Some explanations are suggested for these differences.