The purpose of this study is to test different treatments to reduce relapse for drug-abusing adolescents who have completed family therapy. Adolescents receive 12 weeks of family therapy, designed to strengthen family relationships and develop skills for helping the adolescent avoid drug use. Then they are randomly assigned to receive one of three eight-week follow-up treatments: phone calls from a project therapist, group therapy, or a customized schedule of therapist visits with the adolescent, the adolescent's family and teachers, coaches, probation officers and others who can help the adolescent reach or maintain abstinence. Families are assessed using questionnaires and interviews before, during and after treatment, to provide information about family functioning, the adolescent's drug use, the adolescent's peers and other factors that may contribute to treatment success or failure. Adolescents also provide urine specimens for drug screening at assessment visits. Study investigators expect the study will show that a functional family environment and insulating adolescents from the influence of peers who use drugs will help prevent relapse for adolescents who have received family therapy.