A 74-year-old man was admitted because of appetite loss in November 1999. A gastric ulcer was diagnosed, and a H2 blocker was given. He had had appetite loss since July 1997 and had experienced epigastric discomfort since October of 1997. On admission, hepatic and pancreatic lymph node swelling was detected by ultrasonography of the abdomen. Physical examination revealed a palpable mass in the middle region of the upper abdomen as well as gynecomastia. Laboratory findings showed high serum levels of hCG (11,700 mIU/ml) and high urinary levels of hCG (1,600 mIU/ml). Upper gastrointestinal endoscopy showed a gastric cancer of Borrmann type 3 in the posterior wall of the middle body. A biopsy revealed a moderately differentiated adenocarcinoma. hCG immunoreactivity was not seen in the cancer tissue. A contrast-enhanced CT scan of the abdomen revealed multiple lymph node swelling in the hepatic and pancreatic lymph nodes. There was a low-density area suggesting liver metastases. No other primary carcinomas were not detected. We believe that the gynecomastia was due to the hCG-producing tumor. The patient died 2 months after diagnosis.