Research Summary Just four decades ago, the predominant narrative in crime prevention and rehabilitation was that nothing works. Since that time, criminologists have accumulated a wide body of evidence about programs and practices in systematic reviews. In this article, we summarize what is known in seven broad criminal justice areas by drawing on 118 systematic reviews. Although not everything works, through our “review of reviews,” we provide persuasive evidence of the effectiveness of programs, policies, and practices across a variety of intervention areas. Policy Implications It is time to abandon the idea that “nothing works,” not only in corrections but also in developmental, community, and situational prevention; sentencing; policing; and drug treatment. Nevertheless, key gaps remain in our knowledge base. The results of systematic reviews should provide more specific guidance to practitioners. In many areas few randomized evaluations have been conducted. Finally, researchers, through their studies and systematic reviews, must pay more attention to cost–benefit analysis, qualitative research, and descriptive validity.