Juveniles were eligible for participation in this study if they had received services from one or more of five public service sectors in San Diego County, CA.: specialty alcohol/drug services, the juvenile justice system, mental health services, the Department of Social Services/Child Welfare, or special education for seriously emotionally disturbed youth. The 420 randomly sampled youth were ages 13-18. Youths were interviewed between October 7, 1997, and February 1, 1999, as part of a comprehensive computer-assisted interview about their need for and use of mental health and substance-abuse services. The youths were assessed with the Diagnostic Interview Schedule for Children-IV and the Composite International Diagnostic Interview-Substance Abuse Module. The types of services received were examined in relation to each youth's age, sex, race/ethnicity, mental health disorders, functional impairment, and type and number of substance-use disorders. The study found that non-White youths were less likely to receive the least restrictive services, and they were more likely to receive services in juvenile justice settings. A number of substance-use disorders were positively related to outpatient, residential, and juvenile justice services. Marijuana use was positively associated with the use of outpatient services, and stimulant use was negatively associated with the use of such services. There is a clear need for youth systems of care to improve policies and procedures for the identification and treatment of substance-use disorders. The findings have exposed how racial/ethnic differences and differential involvement with multiple substances can impact service patterns for adolescents. 3 tables and 58 references