Reports of the presence of two histologically different neoplasms in one organ are still unusual. We experienced a rare case of coexisting primary malignant lymphoma and adenocarcinoma of the stomach. A 66-year-old woman was admitted in April 1983 because of weight loss and epigastralgia. Several examinations including gallium scan, upper GI endoscopy, biopsy and touch cytology of the stomach, were performed, and she was diagnosed as having primary malignant lymphoma (noncleaved, large cell type) of the stomach. After the administration of 20 mg of vincristine, 6,000 mg of cyclophosphamide, 1,000 mg of prednisolone and 150 mg of Adriamycin, she improved to complete remission in August 1983. In February 1984, she received gastrectomy because of stenosis of the esophagogastric junction. Microscopic examination of the ulcerated lesion at esophagogastric junction revealed moderately differentiated tubular adenocarcinoma infiltrating to the subserosa. Despite chemotherapy, peritonitis carcinomatosa developed, and the patient died of cachexia in July 1984.