Eighty gastric cancer patients with peritoneal dissemination were analyzed to evaluate the effect of intraperitoneal chemo- and/or immunotherapy on abdominal ascites. Among them, 19 were treated with intraperitoneal chemo- and/or immunotherapy, and 21.1% of them showed decreased ascites and better QOL. Patients treated with intraperitoneal administration with OK-432 showed good survival. Among patients with OK-432 administration, those receiving postoperative chemotherapy showed better survival than those given immunochemotherapy. Conversely, among patients with chemotherapy, those given postoperative immunochemotherapy showed better survival than those on chemotherapy. Patients with HLA-type I and III, and those with preoperative normal immune status showed good response when they received intraperitoneal therapy.