The evolution of law enforcement is traced from the Code of Hammurabi through the 1970's. Following a discussion of the need for modifying and redefining police responsibilities in response to social change, the individual role of the police officer on the streets in maintaining order and controlling crime is assessed. Statistical data are presented for all aspects of law enforcement activities, including police to population ratios, expenditures, education criteria, and occupational hazards. The historical development of law enforcement organizational structures is reviewed, and the specific line and staff functions of a law enforcement agency are outlined. Also covered is the relationship between police and other components of the criminal justice system. Discussion concerning the police officer first examines the police personality and defines various organizational arrangements, including team policing. The relations between police and the community are addressed, with attention to perceptions of the police by different classes, age groups, and minorities. The need for professionalization in law enforcement is emphasized in a discussion of educational requirements, training, advancement, and professional organizations. Behavior problems stemming from the police subculture are also considered. A discussion of law enforcement technology is divided into the following categories: aids for line officers involving recordkeeping, personal equipment, and transportation; support, such as communications equipment and the crime laboratory; and management information systems. The final volume briefly details common law enforcement operations -- crime prevention, detection and apprehension of offenders, control of noncriminal activities such as traffic, and administration. References accompany individual chapters. Statistical tables and organizational charts are provided.