Birthweight, gestational age, and Apgar scores of drug-exposed infants were compared to those of drug-free infants using data collected from birth certificates. Infants born to abusers of opiates and cocaine as well as opiates and cocaine together were also compared to one another. The presence of adverse neurologic signs, need for intensive care, and length of hospitalization after delivery were compared among different types of drug-exposed infants using data collected in a program for infants at risk for developmental delay. Infants of all drug abusers weighed an average of 423 g less than controls; mean gestational age for infants in the different drug groups ranged from four to ten days less than for controls. Opiate-exposed infants were significantly more likely to show adverse neurologic signs than were those with exposure only to cocaine, and were more likely to need intensive care. Infants of polydrug (cocaine + opiate) abusers fared worse than infants born to abusers of single drugs with respect to birthweight, gestational age, and length of hospital stay. Outcomes for infants of "crack" abusers were worse than those for infants exposed to other forms of cocaine with respect to birthweight and adverse neurologic signs. Our findings suggest that special outreach and follow-up efforts may be needed to facilitate the optimal development of these infants.