Sugars in capillary blood were measured during the first hours of life in full-term infants delivered vaginally and by cesarean section. Pretreatment with dextrose solution for mothers delivered vaginally did not affect the course of the sugar in blood significantly Pretreatment with dextrose or saline solution for mothers delivered by cesarean section produced significant differences in the course of the infants' sugar in blood when compared to each other. Full-term infants delivered vaginally who were more than 6 hours old had a greater hyperglycemic response to glucagon, 30 µg/kg, than infants less than 3 hours of age. Full-term infants delivered by elective cesarean section without previous labor responded to 30 µg/kg of glucagon with a diminished hyperglycemia as compared to infants delivered vaginally. An exposure to labor influenced the neonates' response to glucagon, whereas neither pretreatment of the mother nor the course of sugar in blood were associated with this response. With large doses of glucagon, 300 µg/kg, the response differences associated with mode of delivery and maturity were not found to be significant.