General anesthesia was compared with regional anesthesia as to its effects on mother and fetus in 2,856 vaginal deliveries at term. General anesthesia was used in 2,019 cases, and in 1,022 of these the anesthetic was cyclopropane. Biochemical data were obtained from maternal and fetal blood. In addition, three methods of evaluating the condition of the infant at birth were employed, including a special score based on certain cardiorespiratory and neuromuscular observations. The blood of most infants delivered of mothers receiving cyclopropane contained this gas in demonstrable amounts, but there was no obvious correlation between its concentration and the score noted for the infant. The gas probably induced a mild, readily reversible central narcosis. There was no biochemical evidence that it depressed placentral function, but infants born with the mother undergeneral anesthesia, specifically cycopropane, were more depressed than those born with the mother under regional anesthesia.