The study found that current psychiatric symptoms and developmentally relevant factors, but not psychiatric diagnosis at treatment entry, predicted which youth returned to alcohol and drug use in the 6 months following treatment. A return to substance use within 6 months after treatment commonly occurred in the company of same-aged or older peers, most often while socializing with friends they knew prior to treatment. Youth with both substance-use and mental-health disorders relapsed when dealing with temptation. A large portion of these youth also indicated that social pressure was an important factor in the specific context for failing to resist temptation. The psychiatric symptoms of youth with mental-health disorders placed them at highest risk for relapse under social pressure. Anxiety and depressive symptoms apparently reduced a youth's ability to maintain abstinence from substance use. The findings suggest that attention to the specific symptoms of youth psychopathology within the context of developmental stressors and abstinence-maintenance motivation is necessary in order to prevent a return to substance use for youth with both mental-health disorders and substance-abuse disorder. Study participants were 103 adolescents who reported at least 1 substance-use incident within the first 6 months after completing treatment. Each youth had at least one Axis I DSM-III-R disorder. 2 tables and 34 references