The TC views drug abuse as deviant behavior that reflects impeded personality development that requires a global change in the individual through an integration of conduct, feelings, values, and attitudes associated with a socially drug-free lifestyle. The original study sample included all clients admitted to six drug-free residential therapeutic communities across nine sites for treatment of drug/alcohol abuse and concomitant problems. Of the 485 adolescents who completed a posttreatment follow-up interview, the majority were male (71 percent) and European-American (60 percent). Approximately 31 percent graduated or completed the residential phase of treatment; 52 percent dropped out of treatment, and the remainder were terminated for a variety of other reasons (e.g., referred elsewhere and discharged for behavioral reasons). The measures for the present study were derived from admissions (baseline) and 1-year posttreatment (follow-up) interviews. One-year posttreatment outcome data are described for 485 adolescents and separately for treatment "completers" and "noncompleters." The majority of the sample had been mandated to treatment by the criminal justice system. Most reported marijuana as their main drug of abuse. There were significant reductions in drug use and criminal activity, and the most consistent predictors of positive outcomes were completion of treatment and not associating with deviant peers posttreatment. The findings were obtained on a treatment sample for whom there is relatively little research to date; they provide important evidence for the effectiveness of the therapeutic community for this population. 6 tables and 30 references