In the following study, the authors examine factors that explain citizen participation in crime prevention activities in Boston. Using survey data from a random sample, census data, and official crime and arrest data, the authors identified a wide range of individual- and community-based indicators that could potentially explain citizen involvement in crime prevention. Findings revealed that citizen involvement in collective crime prevention does indeed vary by the risk level of a particular neighborhood, with high-risk neighborhoods demonstrating higher rates of involvement than low- to moderate-risk neighborhoods. The authors also found that the factors that explained citizen participation varied by the risk level of the neighborhood. Overall, this research demonstrated that in high-risk neighborhoods, citizen involvement in crime prevention activities is affected by the unique blend of personal, parochial, and public social control mechanisms operating in these areas. (Contains 1 figure, 4 tables and 8 notes.)