Subjective indicators of police performance include the judgments of community residents about police effectiveness in countering crime and police adherence to ethical standards. Even though public attitudes toward and views of police may not be in accordance with objective measures of police performance, public attitudes toward the police influence citizen behavior, particularly regarding citizens' compliance with the law and their willingness to cooperate with the police. Before public views about police legitimacy can be assessed, included in evaluation models, and tracked over time, they must be measured. Two approaches have been used in measuring police legitimacy. The first measures overall public judgments about the police and the law. These judgments reflect the key issues of obligation to obey, trust and confidence, and feelings. The second set of questions addressed to citizens in community settings measures the public's views about aspects of the police and police behavior that are potentially related to police legitimacy. Three aspects of police behavior have been measured: police performance in fighting crime; equality or inequality of the distribution of police service and/or police treatment of citizens across individual and group characteristics; and police adherence to standards of appropriate conduct when dealing with the public. To test the importance of various indexes of legitimacy, researchers should conduct a validation study in which a link between elements of legitimacy and important criteria behaviors is established empirically. To do this, studies must measure the various elements of legitimacy and test whether they influence relevant community residents' thoughts, feeling, and behaviors. The studies described in this article illustrate how such a study would be done and the type of results it would produce. 5 tables, 9 references, and a sample citizen survey on aspects of policing