The principal activity that separates the modern police force from other civic organizations is its legal authorization to use justifiable force. The primary distinguishing characteristic of almost all police tasks is not a concentration on crime but an officer’s legitimate capacity to use violence to carry out the lawful directives of public officials or to maintain civic order. Yet how this force is used remains an extremely divisive issue. The Federal courts have made extensive efforts to regulate the use of force by police officers. Regarding the use of deadly force, the government can take the life of an individual only when an officer has good reason to suspect that the individual’s actions present immediate danger to others in close proximity. On excessive but nondeadly force, the standard holds that the use of force must be “judged from the perspective of a reasonable officer coping with a tense, fast evolving situation.” The police are subject to civil lawsuits alleging the use of excessive force at either the State or Federal level. To be successful in a Federal suit, the plaintiff must prove that the officer’s actions caused a deprivation of a constitutionally guaranteed right. The public is also protected from excessive force by criminal codes at both the State and Federal levels. Violent police-citizen encounters that do not involve deadly force are not well documented by police departments. The two most common accounts for the use of force focus on either the individual characteristics of officers or the situational conditions that make violence in police-citizen contacts more likely. Research shows that local community arrangements, the organization of police departments, and the resulting formal and informal rules departments use to control their employees seem to provide the best explanations for the likelihood that officers will use inappropriate force. 1 figure, 1 table, 86 references