The impact evaluation revealed significant reductions in crime and disorder calls for service, and systematic observations of social and physical disorder at the treatment places relative to the control places uncovered no evidence of significant crime displacement. A mediation analysis of the isolated and exhaustive causal mechanisms that comprised the strategy revealed that the strongest crime-prevention gains were generated by situational prevention strategies rather than by misdemeanor arrests or social service strategies. The article notes that dealing with physical and social disorder to prevent serious crime has become a central strategy for policing, and evaluates the effects of policing disorder, within a problem-oriented policing framework, at crime and disorder hot spots. In contrast to previous “broken windows” studies, this article indicates that dealing with disorderly situations requires an array of activities not captured in one-dimensional misdemeanor arrest measures, and this study advanced the collective knowledge on the effects of policing disorder through use of a randomized block experimental design in conjunction with qualitative indicators on local dynamics. The officers studied engaged "shallow" problem solving and implemented a strategy that more closely resembled a general policing disorder strategy rather than carefully designed problem-oriented policing responses. Thirty-four hot spots in Lowell, MA were matched into 17 pairs, and 1 member of each pair was allocated to treatment conditions in a randomized block field experiment. Tables, references