In combating crime in America, little attention has been paid to keeping children from becoming criminals. What benefit might be realized from such an approach, & at what cost? Working from limited data on program efficacy & on criminal careers, the authors of this report made rough estimates of the costs & benefits of four early interventions--prenatal home visits by child care professionals, followed by four years of day care; training for parents with young children who have shown aggressive behavior; incentives to induce disadvantaged high-school students to graduate; & monitoring & supervising young delinquents. All except the first appeared to be at least as cost-effective as a popular but very different approach to crime reduction--California's "three-strikes" law. The advantages of parent training & graduation incentives in particular are so large that some advantage is likely to be found even under assumptions differing substantially from those made here.