Purpose: This study examined the associations between social, behavioral, and environmental factors and adolescent parenthood. Methods: We analyzed data from a subsample of participants, 18-30 years of age (n = 7,937), who took part in the 2001-2002 National Epidemiologic Study on Alcohol and Related Conditions, a nationally representative survey of adults. An extended Cox proportional hazards model was used to model time until becoming an adolescent parent (i.e., age at which first child was born if ≤18 years). Predictor variables of interest included initiation of alcohol, marijuana, cocaine, and daily cigarette use, age of earliest conduct disorder symptom, having a parent with alcohol and/or drug problems, parental death, divorce and/or separation, race/ethnicity, and gender. Results: Several variables were associated with adolescent parenthood, including initiation of daily cigarette smoking, age of first antisocial/conduct disorder symptom, and race/ethnicity. Parental alcohol/drug problems and parental death were also associated with adolescent parenthood for women. A significant interaction between initiation of daily cigarette smoking and ethnicity was present for women. Daily cigarette smoking was associated with adolescent parenthood to a greater degree than nondaily cigarette smoking for white and Hispanic women but not African American women. No significant associations were found between adolescent parenthood and initiation of drinking, marijuana, or cocaine and parental divorce/separation. Conclusions: Prevention efforts should focus on adolescents who are at highest risk of adolescent parenthood.