Earlier attempts at police professionalization through specialized assignments, technological advances, and organizational reform did not halt rising crime rates nor improve public perception of police effectiveness. They were strategies oriented to reactive policing and repressive law enforcement. In some communities, however (Chapeltown, Cranfield, Ulster), police officer participation in community projects has engendered trust between patrol officers and neighborhood residents, achieving crime preventive results. Among the examples of successful police-community cooperation are the formation of a football team that channeled potential juvenile troublemakers into sports, and Ulster's Blue Lamp Discos, where local youths congregate with the support of various social services, including the police. A crime-prone, potentially explosive, deteriorating neighborhood of Birmingham, populated by immigrants and fraught with social problems, has also become more calm through efforts of the police and other agencies. A variety of self-help projects are encouraging mutually supportive interaction between authorities and the citizenry. Preventive work is a crucial function of police service, to be pursued in concert with other groups working in the interests of the community. The preventive movement depends on grass-roots incentives along with government support. Preventive police activities cannot substitute for traditional law enforcement, but they do provide a complement to the reactive strategies of crime control. The bibliography cites 14 research studies of specific British crime prevention programs; footnotes are also given.