Forty-three of fifty babies with birth weights 1,100 gm or less were hyperglycemic with serum glucose levels exceeding 125 mg/100 ml while receiving parenteral glucose. Serum glucose levels exceeded 300 mg/100 ml in 36 of these 50 babies. Hyperglycemia was most frequent in the 24 hours after birth and was also related to high rates of glucose infusion (> 0.4 gm/kg/hr from birth) as well as parenteral glucose administration in the absence of oral supplement. These data attest to the fragile nature of glucose metabolism in infants of very low birth weight.