Teenage mothers are more likely to use drugs, and their children are more likely to use substances and become pregnant during adolescence. Teenage mothers' substance use may play a role in the intergenerational risk for adolescent pregnancy. Pregnant adolescents (12-18 years) were seen during pregnancy and postnatal years 6, 10, 14, and 16 (n = 332). Teenage mothers reported on substance use and family characteristics. The offspring reported substance use (starting at age 10) and sexual behavior (ages 14 and 16). Prenatal alcohol exposure was associated with offspring (a) having a risky first sex partner and (b) multiple sex partners in the past year. Heavy maternal drinking during childhood was associated with offspring reports of a risky first sex partner and early teenage pregnancy. Findings from this unique birth cohort have implications for alcohol prevention efforts with girls during and after a teenage pregnancy and interventions to prevent risky sex in high-risk youth.