Multiple-drug (OK-432, PSK and SPG) immunotherapy and chemotherapy provided remission of symptoms for 36 months in a patient aged 21 years suffering scirrhous gastric carcinoma associated with carcinomatous peritonitis in which direct infiltration to the pancreas, retroperitoneum and the left colon was observed. A remarkable improvement with time was observed by endoscopic and roentgenographic observation, and a substantial improvement was also observed in the NK-cell ratios of lymphocyte subsets of the OKT series in relation to immunologic parameters. A tumor necrosis factor [TNF]-like substance was thought to have been induced by multiimmunotherapy in this case.