Glycogen storage disease type Ia is caused by a deficiency of glucose-6-phosphatase (G6PC), which leads to glycogen accumulation in many organs including liver. We could diagnose a case of glycogen storage disease type Ia with molecular genetic analysis. A 17-year-old man visited Yeungnam university hospital because of abdominal discomfort. Clinical features were characterized by short stature, hepatosplenomegaly, accompanying hypoglycemia, hypercholesterolemia, hyperuricemia. Liver needle biopsy disclosed compatible findings of glycogen storage disease. Molecular genetic analysis of the G6PC gene was performed by direct sequencing method. We identified two mutations within the exon 5 of the G6PC gene, 727G>T and 743G>A. We report this rare case with a review of the literature.(Korean J Med 71:91-96, 2006)