A 67-year-old male was admitted to Kagoshima University Hospital and received distal gastrectomy with D1 lymph node dissection under the diagnosis of early gastric cancer. Five years later, a retroperitoneal tumor 12 cm in diameter was detected by abdominal CT. Although the tumor was curatively resected, rapid recurrence was identified in the same retroperitoneal space. Chemoradiation therapy (radiation 50 Gy and bleomycin) for residual tumor was performed, but the tumor rapidly grew. The patient was given cisplatin (CDDP) and gemcitabine (GEM) following CPT-11 treatment. The recurred tumor was remarkably shrunken and completely regressed after eight courses of the chemotherapy. The retroperitoneal tumor was finally diagnosed as lymph node relapse from undifferentiated gastric cancer. This rare case of undifferentiated gastric cancer showed a complete lymph node response following combination chemotherapy of CDDP and GEM. Combination chemotherapeutic regime with CDDP and GEM seems to be useful for treatment of undifferentiated gastric cancer.