Data were provided by the Police Services Study, part of which consisted of intensive data collection in 24 departments in the metropolitan areas of Rochester, N. Y.; St. Louis, Mo.; and Tampa/St. Petersburg, Fla. Three variables had a statistically significant and interpretable effect on both forms of aggressiveness. Ambition, in the context of an organization that rewards a legalistic style of policing, appeared to lead officers to conduct suspect stops more frequently and to make more traffic stops. Upwardly mobile patrol persons in other departments were neither more nor less prone to be aggressive. Experience, as hypothesized, depressed these proactive behaviors. The magnitude of the effect was not greater in legalistic departments. The amount of discretionary time available to an officer had a large effect on aggressiveness. Three other individual characteristics had a significant effect on suspect stops but not on traffic stops; officers with high morale, a college education, and who were black made suspect stops more frequently. The deployment of patrols in two-officer units appeared to promote suspicion stops, but not traffic stops. Close supervision by departments whose chief is committed to professional doctrine inhabits aggressiveness. Officers in legalistic departments were not significantly more aggressive. Taken together, the results tentatively suggest that organizational arrangements can affect the two forms of aggressive patrol that were examined. Two tables, footnotes, and 17 references are supplied.