Immediate processing of blood and the proper analytical procedures are necessary to obtain reproducible values for glucose in blood in premature infants. Expected levels of glucose in blood in premature infants the first 2 months of life may vary between 20 and 100 mg/100 ml after a 3 to 4½ hour fast on a normal diet. Replicate values of glucose below 20 mg/100 ml may be associated with symptoms of hypoglycemia. The level of glucose in blood the first week of life is influenced by the birth weight, race, and sex of the premature infant. Illness and gestational age could not be correlated with statistically significant differences in levels of glucose.