Fourteen women undergoing elective cesarean section were anesthetized with enflurane for induction and maintenance of anesthesia. Blood enflurane and serum inorganic fluoride levels were studied in the mothers at delivery and in the neonates at delivery and in the early neonatal period. Also neonatal urinary excretion of inorganic fluoride was determined. Renal function of the neonates was tested with a sodium load at the age of 1 day. Enflurane showed the expected distribution between mothers and neonates. The enflurane level of the neonates declined rapidly after delivery. Serum inorganic fluoride level increased significantly in the mothers from start of anesthesia until delivery. The neonatal level was lower and did not reach the level of neonates in areas with a high natural fluoride content in drinking water. The level of inorganic fluoride in urine was higher than the corresponding serum level, indicating an inorganic fluoride concentrating effect of the neonatal kidney. The difference between urinary excretion and serum content of inorganic fluoride showed neonatal metabolism of enflurane. The urinary sodium excretion did not differ from that of infants delivered without halogenated inhalation agents given to the mothers.