This Field Guide is an effort to support USAID officers and other practitioners in the Latin America and Caribbean region who are working on citizen security. It provides a conceptual framework for understanding crime, violence, and prevention as part of broader citizen-security systems; evidencebased information about effective interventions to prevent crime and violence; and practical advice and tools on how to design, implement, measure, and evaluate crime and violence-prevention and citizensecurity projects. The guide incorporates the research findings of academic and development practitioners in an analysis of crime and violence in the region.