Data from 10 large jurisdictions show both that police shootings have declined in recent years and that the rates of police shootings vary significantly across different jurisdictions. External environmental differences do not explain these variations, but police agency philosophies and policies appear to play a significant role. Data from research now in progress in New York City and Philadelphia show that earlier differences in police shooting rates in those two cities were largely a result of the relatively high frequency of apparently elective shootings by members of the Philadelphia Police Department. Clearer policies or more objective enforcement of existing policies could reduce police shootings. Although these measures might not affect crime rates, they will improve police effectiveness in their main responsibility, which is to protect life. Tables, notes, and 22 references.