While extensive research exists, the field lacks a current and translational synthesis of what works to reduce youth group and gun violence. In response, the Urban Institute developed a research-based practice guide to inform local government, law enforcement, and community-violence-intervention stakeholders as they implement new antiviolence interventions and refine existing ones. To inform the development of the guide, Urban researchers conducted a comprehensive literature synthesis of research on violence reduction interventions and conducted a scan of interventions representing well-known antiviolence models and other innovative strategies. Drawing on the findings from the literature synthesis and scan of practice, the practice guide presents recommendations around nine practice areas related to building an infrastructure to support a multi-faceted antiviolence strategy and implementing effective violence reduction programs.