The analysis addressed whether treatment had positive effects on juvenile delinquency prevention. It was found that treatment modality was the most important factor in methodological differences among studies. More behaviorally specific and structured treatments generally produced larger effects than traditional counseling and casework approaches. Effect sizes for more successful treatments represented reductions of 20 percent or more in the recidivism of treated juveniles compared to control juveniles. In addition, treatment had positive effects on psychological, interpersonal, school participation, academic, and vocational outcomes. Such changes, however, did not correlate across studies in a way that indicated these dimensions were uniformly improved by treatment. Rather, it appeared that reduced juvenile delinquency was regularly accompanied by school participation. School participation, in turn, was associated with positive effects on psychological and interpersonal variables. 21 references and 7 tables