PURPOSE: This study is to determine the frequency, onset age, and the proper duration of evaluation in fullterm large for gestational age (LGA) newborn infant. We also compared risk factors between hypoglycemic and euglycemic newborns. METHODS: 77 term newborns from non-diabetic mothers who were greater than 90 percentile on Lubchencho growth curves were included in this study. Blood glucose levels were checked at age 1, 2, 3, 6, 12, 24, 36, 72, 96 hours and cord blood with rapid strip test. Hypoglycemia was defined as a serum glucose less than 35 mg/dL at less than 3 hours, less than 40 mg/dL between 3 to 24 hours, and less than 45 mg/dL at greater than 24 hours of age. RESULTS: In 77 fullterm neonates with LGA (4,185+/-224 g, 39+/-0.9 wk), frequency of hypoglycemia was 9 case (11.7%) and 3 case of them (3.9%) had clinical symptoms of hypoglycemia. The mean onset age and mean serum glucose level were 2.56+/-2.13 hour and 34+/-6 mg/dL. Glucose level started to decrease in 1 hour and showed lowest at 2 hours. No hypoglycemic patients were noticed after 6 hours of life. There were no significant differences in delivery type, sex, preeclampsia and meconium staining between hypoglycemic and euglycemic newborns except maternal body weight greater than 80 kg (P<0.05). CONCLUSION: Screening of hypoglycemia after 6 hours of age in fullterm LGA newborn infants might not be necessary. And neonatal hypoglycemia should be considered if maternal body weight greater than 80 kg.