This study examined the influences of individual and social risk factors on alcohol and marijuana use among a sample of foster care adolescents. Data were collected through baseline structured interviews with 320 adolescents (aged 15-18 years) who resided in foster care placements and participated in a larger evaluation study of an independent living program. Approximately 40% of the adolescents reported alcohol use, 36% reported marijuana use, and 25% reported both alcohol and marijuana use during the 6 months prior to the interview. Final logistic regression models indicated that having friends who used marijuana and other substances and having skipped school remained most predictive of using alcohol, marijuana, or both alcohol and marijuana. Recommendations for substance abuse prevention and treatment for these vulnerable adolescents are proposed.