Objective: To evaluate the association between prenatal alcohol exposure and the rate of conduct disorder in exposed compared with unexposed adolescents. Method: Data for these analyses are from a longitudinal study of prenatal substance exposures. Women were interviewed at their fourth and seventh prenatal months, and with their children, at birth, 8 and 18 months, 3, 6, 10, 14, and 16 years postpartum. Offspring were interviewed with the Diagnostic Interview Schedule-IV; maternal and adolescent diagnoses were made using "DSM-IV" criteria at age 16 years. The sample was 592 adolescents and their mothers or caretakers. Results: Prenatal alcohol exposure is significantly associated with an increased rate of conduct disorder in the adolescents. This effect was detected above an average exposure of one or more drinks per day in the first trimester. The effect remained significant after controlling for other significant variables including measures of the environment, maternal psychopathology, and other prenatal exposures. Conclusion: Prenatal alcohol use in the first trimester is a risk factor for conduct disorder in the exposed offspring. (Contains 4 tables and 1 figure.)