The number of persons employed in private security grew rapidly during the 1960's, and 36,525 persons were estimated to be employed in private security in 1971, compared to 39,724 public police personnel in that same year. Private security persons can be defined as persons employed in security occupations other than the military and the public police and other public officials with peace officer status. Private security police investigate crimes, maintain order, and respond to emergency and crisis situations. Unlike public police, they are also responsible for enforcing private regulations, e.g., access to certain areas. When citizens are policed by private security, such policing is in the interests of the security person's employer; whereas, public policing is in the interest of citizen protection. Private security persons usually only have the powers, rights, and duties of private citizens or the powers delegated to them by their employer who often is 'the owner or a person in lawful possession of property,' which makes citizen powers of arrest more extensive. In practice, private security persons have powers of arrest that equal those of public police, since they can act in the name of the employer to detain persons for trespassing even when no other crime has been observed. Private security services are regulated by licensing. Tabular data, 14 suggested readings, and 7 notes are provided.