While correlational studies of neighborhoods and citizen participation are numerous, there is a paucity of rigorous experimental evaluations that test the proposed 'Implant Hypothesis,' that is, that collective citizen participation (and the social processes it allegedly activates) can be implanted in neighborhoods where it does not currently exist. However, there are both theoretical and empirical reasons to challenge some of the basic assumptions underlying the Neighborhood Watch approach to reducing crime, reducing fear of crime, and restoring a sense of community. The hypothesis that Watch programs increase fear of crime and may have other effects is examined. The implications of this assessment for theory development and public policy are explored. (Author abstract)