The traditional measures of police effectiveness in fighting crime are not only inadequate for measuring the performance and effectiveness of the broader police role but also for measuring even the more narrow, crime-focused functions of the police. The two approaches to improving the measurement of either police performance or the effects of policing involve improving the technology or methodology of measurement and improving the conceptualization of that which is to be measured. The use of official crime, arrest, or other organizational data should be avoided in either comparative studies or in those in which data are to be aggregated across communities. The most reliable analyses will be experimental studies conducted on a site-by-site basis. Based on results derived from such analyses, it is possible to take into account those contextual or organizational characteristics that may influence either police performance or the effects of policing. The next most reliable method will be longitudinal studies done site-by-site, with particular attention to contextual and organizational factors. Perhaps the greatest improvement in measurement, however, will result from clearer thinking about what is to be measured. Intermediate goals that the police can attain must be specified, along with strategies directly linked to those goals. These intermediate goals are located conceptually between police activities or inputs and the ultimate goals of crime reduction and increased citizen comfort. Intermediate goals are preventing crime, managing crime, and penalizing crime. Penalizing crime refers to all police efforts to increase the cost of committing crime, and managing crime involves containing the effects of crime. Fifty-three references are provided.