A total of 110 infants born to mothers who were either in a methadone maintenance program, using heroin, or recently detoxified, were studied during the neonatal period. Of these infants, 93.6 per cent developed withdrawal symptoms. No significant differences were determined in therapeutic response among those infants treated with methadone, phenobarbital, and diazepam. There was a significant reduction in the frequency of withdrawal symptoms among infants born to mothers whose methadone dose at time of delivery was less than 20 mg (17.9 per cent). It is suggested that reduction of methadone dosage in late pregnancy results in reduced incidence of withdrawal but must be carefully carried out.