A 59-year-old man was admitted to the hospital because of recurrent severe hypoglycemia, who had undergone a total gastrectomy for a cancer of the cardiac part of stomach about one year before. During hypoglycemia the plasma level of immunoreactive insulin was under 2.5μU/ml. Adrenal and liver functions were normal. The serum level of IGF-I was 34ng/ml (normal range, 88_??_240), and IGF-II was 550ng/ml (374_??_804). So the ratio of IGF-II to IGF-I was higher than normal. Western immunoblot assay showed high-molecular-weight IGF-II in the serum. Abdominal CT visualized multiple heterogeneous tumors in both lobes of the liver. Percutaneous needle biopsy disclosed metastasis of adenocarcinoma, and immunohistochemical staining for IGF-II was positive in tumor cells in both the liver and stomach. We conclude that the most likely cause of this patients hypoglycemia was IGF-II produced by the metastatic liver tumor from the gastric cancer.