This report assesses the cost effectiveness of several crime prevention strategies that involve early intervention in the lives of people at risk of pursuing a criminal career. Four different approaches are examined: (1) home visits by child care professionals beginning before birth and extending through the first 2 years of life, followed by 4 years of day care; (2) training for parents and therapies for families with very young school-age children who have shown aggressive behavior or begun to act out in school; (3) 4 years of cash and other incentives to induce disadvantaged high school students to graduate; and (4) monitoring and supervising high-school-age youth who have already exhibited delinquent behavior. The efficacy of these pilot programs is estimated, figuring penalties in effectiveness for scale-up and decay. Larger penalties are calculated for the two earlier interventions, which have been less tested and which also have more opportunity for decay before children reach a crime-prone age. Estimated costs, which do not take into account savings from preventing incarceration of youth affected by the programs, were compared with those of incarceration. Three of the four strategies (but not home visits) compare favorably in cost effectiveness with incarceration. Research has suggested that crime reduction achieved through incarceration can be substantial, but this study suggests that additional reductions can be achieved through parent training, graduation incentives, and delinquent supervision. For less than a billion dollars, graduation incentives and parent training could roughly double crime reduction if they are as effective as these analyses suggest. Two appendixes present some research findings on early intervention and detailed cost effectiveness results. (Contains 8 figures, 28 tables, and 66 references.) (SLD)