The focus of the review is on actual programs that have been evaluated under experimental or quasi-experimental designs. Attention is also given to economic evidence of early developmental prevention based on leading studies that have used mathematical modeling techniques. The review found that research on the economic costs and benefits of early developmental prevention of delinquency is limited; however, existing cost-benefit analyses indicate that the evaluated programs show promise as an economically efficient means of reducing delinquency. Analysis has found that such programs can match or exceed the economic value of other approaches to delinquency prevention, notably deterrence-oriented punitive sanctions. Further, the cost-benefit analyses of some of these early intervention programs have yielded conservative estimates of the economic benefits; for example, an estimate of the intangible costs to potential crime victims absent the intervention program was often omitted in the calculations. In making recommendations for future research on early intervention programs, top priority is given to greater use of experimental research designs, particularly randomized experiments. For programs that target larger units such as communities, schools, and classrooms, experimental-control designs with before-and-after measures are necessary. The recommended outcome variables for calculating the costs and benefits of early intervention programs are savings for the criminal justice system in not having to process future delinquents/criminals, savings in tangible and intangible costs to potential crime victims and their families, cost savings and improved health from preventing substance abuse, improved educational output, the benefits of stable employment that yields taxes and decreases welfare costs, decreased use of public health services, and more stable and healthy families. 2 tables and 2 notes