A 39-year-old man was referred for epigastric fullness and a mass in the umbilical region. A giant mass was palpated in the epigastric region, while a mass 1 cm in diameter with a hemorrhagic tendency was felt in the umbilical region. Fluoroscopy of the upper gastrointestinal tract and gastroscopy revealed a Borrmann 3 tumor in the upper part of the gastric corpus. The tumor was found by CT scanning to be growing clearly across the wall of the stomach, and the invasion to the transverse colon was suspected by the enema. The tumor was unresectable because of the extensive tumor invasion of the abdominal wall. Therefore, the patient received 2 courses of combined chemotherapy with 5'-DFUR, CDDP, and MMC. As a result, the tumor in the epigastric region was reduced dramatically, and it became unpalpable 6 months after treatment. At the same time, the tumor in the umbilical region disappeared. Both CT scanning and upper gastrointestinal radiography disclosed tumor reduction, and sufficient oral ingestion became possible. The administration of 5'-DFUR has since been continued as maintenance therapy. Aside from transient anorexia and slight leukopenia, the patient developed no symptoms during the treatment period. At present. 2 years and 9 months after starting chemotherapy, the patient is in good health.