The study evaluates the effectiveness of four therapeutic day schools in preventing substance abuse by youths referred by children's protective services and juvenile probation. It also examines factors associated with successful early intervention. Specific objectives are: a. To assess the effect of the intervention strategy on high risk adolescents. b. To test association of substance abuse with behavioral and personality indicators. c. To study the impact of parental attitudes and home environment on the prevention effort and on other outcome measures. d. To develop baseline data for longer term followup. The design includes an experimental group of 100 day school students, and two comparison groups of 100 youths each; one group from an adjacent county with no day treatment program, and the other from among adolescents from the same county who are appropriate for day school referral but who are not sent there for some reason. Both groups will be given a series of achievement and personality tests, and an interview covering drug use, behavioral problems, recreational activities, and attitude toward family, school and authority. The interview/test session will be conducted at intake (or equivalent for comp. groups), 6 months (exp. group only) and 12 months. Parents will also be interviewed at intake and 12 months later. Additional information will come from school and county casefiles. For day school students there will also be behavioral logs and clinical ratings. Factor and cluster analysis will be used to derive meaningful scales and to reduce the number of variables included in the final analysis. A general linear model incorporating multiple regression and analysis of variance/covariance will be used to test the hypotheses derived from the objectives. Results of the analysis will be disseminated to help establish the place of therapeutic schools in the whole prevention/intervention/treatment spectrum, and to clarify the relationship of adolescent substance use with other personal and social factors. The project will also identify the type of youth with whom this intervention is most effective.