A group of eighteen infants which experienced the neonatal abstinence syndrome due to prenatal maternal use of methadone responded adequately to phenobarbital with control of symptoms. By administering the phenobarbital as an initial single loading dose and closely monitoring the blood levels, maintenance dosing could easily be adjusted for variables in infant metabolism and pharmacologic effect. By use of a multifactorial abstinence scoring system, the pharmacologic effects on clinically observed abstinence symptomatology could be closely monitored and correlated with the blood levels. Serum levels of 20-30 mcg/ml were adequate to control all but one infant. Tapering the blood level of phenobarbital to 10-12 mcg/ml and observing no scores over 8 for 72 hours identified the place in time where abstinence was no longer significant and the infant could be discharged without medication.