Specialized private security has been growing more rapidly than both the population and the public police. This expansion represents both a growth in the amount of formal policing and, within the context of this expanded security, a shift in the context of policing from the criminal justice system to other institutions. In performing their similar functions, the police and private security are guided by different objectives. The public police act in the public interest, private security in the private interests of its clients. This contrast between public and private interests finds its expression in a shift in focus away from a concern with 'crime' to a concern with 'loss.' Policy issues relevant to the interface between the public and private security include interchange of personnel and loss of public resources, information exchange, other police/private security cooperation, powers of private security personnel, private security in the workplace, the protection of privacy, and accountability of private security. As private security persons act to preserve both the public peace and the private peace, more of citizens' activities come under the supervision, and often control, of some form of police. Private justice constitutes a major change in the structure of contemporary social control and presents a challenge to the legal framework and liberties of Canadian society. A 55-item bibliography is provided.