Research on situational choices has been limited to classification of general police activities and has not focused on how officers decide how to spend their unassigned time. One of the obstacles to conducting research on police choices of when to intervene is the difficulty of comparing easily observed decisions to intervene with situations where the officer decided against intervention. The literature has identified three dimensions to police-public encounters: legality, control, and personal assistance or support. This report discusses major sources of change in police patrol work over the past decade and their effects. Recruitment and retention of officers is a prime target of forces attempting to change or influence the nature of policing. Of particular interest are characteristics including race, sex, education, health, and moral fitness. The character and quantity of resources available to police departments affect the behavior of patrol officers. Two trends which suggest that police agency structures and administrations will change are department accreditation and problem-oriented policing. A number of alternative patrol tactics have recently gained credence such as the use of one-officer motorized units and differential police response alternatives. In addition, crime attack, community service approaches, and advances in computer technology attempt to improve the patrol officer's effectiveness. Changes in the law and legal environment affect the parameters of police discretion by establishing the limits of legitimate police activity and the consequences of overstepping the bounds. The privatization of policing has been one of the most discussed trends over the past decade and will have a substantial impact on public policing. Finally, the continuing decline of central cities, the influx of large numbers of immigrants, and the AIDS epidemic have important ramifications for police agencies. 124 references.