A 67-year-old male was admitted with the complaint of weakness at hunger early in the morning, when blood glucose was less than 40 mg/dl. The abdominal ultrasonogram and computerized tomogram demonstrated a huge tumor in the right liver lobe. Hypoglycemia disappeared after transcatheter arterial embolization. Then hepatic lobectomy was performed. The tumor was histologically shown to be a fibrosarcoma. Insulin-like growth factor-II was intensely stained in the Golgi area of the tumor cells, suggesting its role in the mechanism of hypoglycemia.