The effect of oral beta-sympathomimetic tocolytic therapy on neonatal serum glucose concentrations in the first several hours after delivery was examined in 12 babies. Hypoglycemia was noted in eight babies, and was sustained over at least a 30-minute period in five. The group with sustained hypoglycemia had a higher cord serum insulin concentration, a lower serum glucose nadir, and a more rapid initial rate of serum glucose disappearance than those babies with normoglycemia or transient hypoglycemia. Sustained hypoglycemia was observed in five of six babies delivered within two days of the termination of tocolytic therapy, but was not present in any of six babies delivered five or more days after the end of tocolytic therapy. Speculations as to the interaction between beta-sympathomimetic tocolytic drugs administered to the mother and fetal and neonatal glucose metabolism are made.