About 12 percent of the population are mentally retarded; 25 percent have some degree of mental disturbance, including 1 percent who are severely disturbed. While the mentally retarded, due to the characteristics of their handicap, are easily caught and are often behind bars, the mentally disturbed harbor potential dangers to themselves and society that may erupt without forewarning. Since the two have totally different causes for their behavior and different treatment needs, it is vital that police officers be able to distinguish between them and provide understanding and appropriate services. The retarded have developmentally limited learning processes in gradations from mild and moderate to severe and profound retardation. Their behavior is often childlike, their muscular coordination undeveloped, their speech slurred, and their information and understanding limited. They may, however, become belligerent if mistreated. Contrary to popular opinion, mentally retarded persons do not become mentally disturbed. The latter disorder arises from emotional stress of intense degree and duration and culminates in a moment of crisis, characterized by distortions of thought, perception, mood, and physical behavior. A series of vignettes illustrate typical behaviors of both mentally retarded and mentally disturbed behavior in public places -- (store, library, street, probation office). Officers are urged to consider what type of handicap is being portrayed and what the officer's response should be.