Recent studies show that the rate of cocaine use by pregnant women in the United States is much higher than realized hitherto, and an increasing number of infants are being born to cocaine-using mothers. In an ongoing research project to study the effects of cocaine on pregnancy outcome, we studied 70 infants born to cocaine-using women. These infants were matched to a drug-free comparison group selected from the population of the same hospital: children of pregnant women of a similar racial and socioeconomic distribution, but with no history or evidence of licit or illicit drug use during pregnancy. Cocaine-exposed infants had lower birth weight, shorter gestation, and a smaller head circumference than control infants. Cocaine-exposed infants also had neurobehavioral abnormalities at initial evaluation and a higher rate of perinatal complications. Toxicological evaluation of urines of neonates born to cocaine-using women showed that benzoylecgonine, a primary metabolite of cocaine, persisted in the urines for as long as 120 h after delivery. We discuss the role of the immature fetal and neonatal system in the clinical and toxicological outcome of the infant, and emphasize that further long-term studies of this will be needed.