While the drive for police agencies to collect data concerning their effectiveness has peaked in recent years, it has become evident that police agencies lack the skills necessary to collect, analyze, and interpret pertinent information. As such, the current article focuses on the type of information necessary for police agencies to evaluate their effectiveness, the way in which that information should be measured, and on the value of comparative performance measurement. A crucial component for organizational learning is the presence of a comparison group that enables an interpretation of evaluation results. The author underscores the importance of recognizing that policing is a multidimensional profession that requires performance assessments on various levels. Once the various dimensions of police performance have been identified, there are several alternatives for collecting information regarding police performance on these dimensions, including general community surveys, citizen contact surveys, and direct observation. Once data have been collected along the identified dimensions, the complexity of the information must be minimized, such as through the use of graphs and composite scores. The differences in the relative importance of the dimensions must be accounted for, perhaps by assigning greater weight to certain dimensions, and fair comparisons must be made. Through this process of accurate performance measurement, police agencies will be challenged to make positive changes and will become true learning organizations. Figure, references