In its 1968 decision in Terry v. Ohio, the U.S. Supreme Court ruled that police could stop and frisk a citizen based on 'reasonable suspicion' that a crime had been committed. This departed from the time-honored standard of 'probable cause.' To examine the effects of police stop and frisk practices, empirical research was conducted in 1972, involving about 500 hours of accompanying police on patrol to observe their use of stop and frisk practices. Evidence indicates that anticipated law enforcement benefits have not been realized from the broader police powers to stop and frisk. The crimes most affected by the practice are burglary, petit larceny, vandalism, marihuana possession, and possession of other drugs, while the more serious crimes of murder, rape, and robbery are not affected. Contrary to predictions that police would no longer use legal subterfuges to detain and frisk a person on the street, police still make use of the charges of disorderly conduct, vagrancy, loitering, curfew violations, and arrests on suspicion, along with vehicle stops for minor traffic violations. However, the feared expansion of police intrusion into citizen privacy, particularly in black communities, has not occurred. An officer on an 8-hour shift rarely uses stop and frisk practices. Thus, neither side in the debate has grounds for its support or disagreement with current stop and frisk practices. A total of 89 notes are listed, and tabular data from the study are provided.