PSN implemented supply-side gun policing tactics, improved Federal prosecution of gun crimes, and held notification forums in which targeted individuals with criminal records were warned of heightened criminal sanctions for gun-crime convictions. Chicago's PSN has been operating since 2002. This assessment of its impact examined relevant data after 10 years of PSN's implementation. Consistent with a previous evaluation, the current study found that several program components were associated with reduction in violent crime in the initial target areas. These impacts, however, were concentrated in the first few years of the intervention. An examination of the effects of PSN in several subsequent expansion areas found no detectable effects. Based on this data collection and analysis, the study suggests that the effects of PSN were diluted as the program expanded to larger areas of the city without an increase in funding and other resources. The evaluation recommends that future research consider PSN's strategies in Chicago that were apparently effective in the early years, and leverage those insights in determining the methods and resources required for sustained effects over the long term. The design and issues in research methodology are described and discussed. 7 figures and 2 tables