Effects on fetal growth and neonatal behavior of cocaine and alcohol use in pregnancy were investigated in infants born to women in a low-income, predominantly black population. Despite the increased use of cocaine by pregnant women and the accompanying public concern, behavioral studies of exposed neonates are limited in number and scope. In most studies, confounding factors (e.g., polydrug abuse, prematurity, infant health status) have not been controlled so the actual effects of cocaine and other drug exposure are not clear. Accordingly, this study investigated effects of prenatal drug exposure although controlling experimentally for other factors known to be associated with poor outcomes in infants: prematurity, other illicit drug use, associated diseases (e.g., sexually transmitted diseases [STDs]), and duration of drug use. In addition, other factors statistically controlled were: experimenter effects, timing of assessment, and effects of duration, amount, and frequency of cocaine, alcohol, marijuana, and nicotine exposure. One hundred and seven full-term infants were assessed at 2, 14, and 28 days using the Brazelton Neonatal Behavioral Assessment Scale (BNBAS) by testers blind to infant status. Growth factors (i.e., birthweight, length, head circumference) were also assessed.