We conducted a Campbell systematic review to examine the effectiveness of problem-oriented policing (POP) in reducing crime and disorder. After an exhaustive search strategy that identified more than 5,500 articles and reports, we found only ten methodologically rigorous evaluations that met our inclusion criteria. Using meta-analytic techniques, we found an overall modest but statistically significant impact of POP on crime and disorder. We also report on our analysis of pre/post comparison studies. Although these studies are less methodologically rigorous, they are more numerous. The results of these studies indicate an overwhelmingly positive impact from POP.