This prospective study examined long-term behavioral characteristics of children whose mothers drank alcohol and/or smoked cigarettes during pregnancy, compared to matched controls. Maternal habits had been assessed by interview during pregnancy; alcoholics and alcohol abusers were not included in this study. Primary outcome measures were naturalistic observations of children's behavior at age 4 in the home setting. Offspring of moderate drinkers (mean = 0.45 oz. absolute alcohol/day during pregnancy) generally were less attentive, less compliant with parental commands, and more fidgety during mealtime than were offspring of occasional and non-drinkers (mean = 0.07 oz. absolute alcohol/day during pregnancy). During storytime, an interaction of maternal drinking and child's sex occurred. The postnatal home environments did not differ as a function of maternal drinking or smoking habits.