Primary choriocarcinoma of the stomach is an extremelyrare and highly malignant tumor. A 60 years old man visitedanother hospital for the chief complaint of the stomachacheand black stools. A large ulcero-vegetative tumoroccupying the gastric body and antrum was seen in theupper gastrointestinal endoscopy. It was diagnosed asgastric adenocarcinoma by endoscopic biopsy. The patientadmitted to our hospital for treatment. The patientwas assessed as a gastric adenocarcinoma complicatedwith hemorrhage. In the exploration, it was observed thatthe mass arising from gastric body was invaded the transversecolon and pancreas. The lymphadenopaties in theceliac axis were conglomerated and had invaded the celiacvessels. A subtotal gastrectomy and an extended righthemicolectomy were performed for palliation. In pathologicalfindings, typical characteristics of two cell pattern consistingof syncytiotrophoblasts and cytotrophoblasts wereobserved. The tumor consisted of only choriocarcinoma.For the definite diagnosis of choriocarcinoma, immunohistochemi-cal tests were performed. Beta-HCG andEMA staining were positive. The patient was invited forcontrol because of gastric choriocarcinoma three weekslater surgery. His serum beta-HCG level was 458 mIU/mL(normal range,