We describe relationships between substance use, conduct disorder (CD), depression, and history of self-injury or suicide attempts, in referred, delinquent, substance involved, adolescent males. Sixty youths (mean age 16.3 years) completed standardized assessments for substance use and other psychiatric disorders, aggressiveness, and social class. All boys met modified criteria for CD. Most had high aggression ratings. Twenty percent had depressive diagnoses. By age 13, 78% had begun regular substance use. Marijuana was the first substance for 42%. The boys had substance dependence on a mean of 3.2 different drugs (usually including alcohol and marijuana), with abuse of an average of one additional drug. CD symptoms began 3.6 years (mean) before regular use. CD symptom count correlated with number of dependence diagnoses, and both of those (but not depression) related significantly to suicide attempt and self-injury histories. Improved understanding of substance involvement in youths with CD may generate more rational prevention and treatment.