To help advance the field’s understanding of what works to effectively address youth group and gun violence, Urban Institute researchers completed an extensive literature synthesis of extant implementation and impact studies. While most studies we reviewed showed the three main types of violence reduction models (focused deterrence, public health, and the Spergel Model of Gang Intervention and Suppression/Comprehensive Gang Model) had mixed results, strategies such as focused deterrence and public health yielded some positive outcomes. Additionally, program components such as case management, enhanced surveillance, outreach workers, and public perception campaigns were associated with effective programs. The findings from the literature synthesis helped inform the recommendations described in Urban’s accompanying practice guide.