As for the non-specific cancer immunotherapy concerned, the effect is limited and local use of immunopotentiators which could collect effector cells around tumor tissues might be the best way of cancer immunotherapy. Intratumoral or intraperitoneal administration of large-dose of OK-432 (100 KE) has been investigated since many years with favorable results. Side effects were minimum with a few days continuing slight fever elevation. From the immunohistological examinations using monoclonal antibodies, participation of killer T cells and NK cells was confirmed after intratumoral administration of large-dose OK-432. On the other hand, after intraperitoneal administration of OK-432, neutrophil leucocytes appeared at first on the 2nd to 4th day and they were followed by lymphocytes on the 4th to 5th day and finally appeared lot of macrophages on the 6th and later days. From the results of in vitro and in vivo experiments, these macrophages seemed to play the leading role in the cytostatic activities after intraperitoneal OK-432 administration. As for the fear of introducing suppressor cells after large-dose OK-432 administration, detailed studies on suppressor activities before and after operation for gastric cancer patients revealed no particular increase of suppressor cell activities after intratumoral and intraperitoneal administration of 100 KE OK-432 as compared with curative resection cases with no OK-432 administration.