The study used patrol observation and neighborhood resident survey data from the Police Services Study. To measure citizens' attitudinal reactions to crime, persons were asked to predict their likelihood of becoming burglary, robbery, or vandalism victims while in their neighborhoods. The police action variables were based on field observations and departmental data on field assignment patterns. Aggressiveness was operationalized as the density of officer-initiated nontraffic encounters in each neighborhood. Police presence was operationalized as the average number of assigned units per square mile in each neighborhood. The most important determinants of fear of crime were offense rates and a household history of victimization. Police confidence-building strategies such as increasing patrol presence may backfire; increased visibility may make citizens more apprehensive. Increased police aggressiveness may soothe some of the citizenry, but in the neighborhoods studied, aggressiveness appeared to impact citizen reactions to only the less serious and less costly crimes. Police can probably have their greatest impact on the fear of crime by reducing the actual level of crime; however, police must also recognize that the tactics used to reduce crime may intensify the fear of crime among certain segments of the population. Further, since citizens with negative attitudes toward the police tended to be more apprehensive about victimization, police efforts to improve relations with the citizenry might also help reduce crime. Tabular data and 30 references are provided.