The editors of this book conclude that, alongside the Campbell Collaborative effort, a program of research of new crime prevention and intervention experiments and quasi-experiments must be initiated in Western countries, using rigorous research designs, including large samples, with long-term follow-up periods, and contain cost-benefit or cost-effectiveness analysis. The main methods for assessing what contributes effectively to evidence-based crime prevention are reviewed; key features of impact evaluation research are reviewed; the relationship between research design and program effects are discussed; and recommendations for improving the state of evaluation research in criminology are put forward, including a description of experimental and quasi-experimental evaluation designs. The main findings and policy implications of the systematic reviews found in this book are summarized, for example, using what works, stopping using what does not, and what is harmful. Finally, a number of important political and policy considerations influencing the use of evidence-based research in the approach to crime prevention are discussed. It is the goal of this body of work to overcome some of the misconceived political and policy barriers and get more of what works in preventing crime by using evidence-based research in policymaking and practice. Appendix, notes, references