Although effective outpatient treatments have been identified for the well-documented negative outcomes associated with delinquency and substance use, effective treatments for youths in out-of-home care are rare. In this study, 12- and 18-month substance use outcomes were examined for a sample of 79 boys who were randomly assigned to Multidimensional Treatment Foster Care (experimental condition) or to group care (comparison condition). The boys in the experimental condition had lower levels of self-reported drug use at 12 months, and lower levels of tobacco, marijuana, and other drug use at 18 months. Limitations and future directions are discussed. (Contains 1 table, 2 figures, and 1 note.)