Sakata, et al. has already reported that the combination therapy of mitomycin-C, carboquone, 5-fluorouracil and OK-432 (MQF-OK therapy) which had established from animal experiments, was exceedingly effective for inoperable human gastric cancer. In this paper, the effectiveness of MQF-OK therapy for inoperable gastric cancer was compared with that of MFC therapy. To perform this controlled study, a "large area" co-operative study group of cancer chemotherapy, composed of 14 institutions in Aomori and a part of Akita prefectures, was organized. From April 1977 to April 1980, patients were registered and 61 cases were evaluable; 31 out of 61 were treated with MQF-OK therapy (MQF-OK group) and the others with MFC group. The background of the cases, such as sex, age etc, was not different significantly between two groups statistically. According to the response criteria of Japan Society for Cancer Therapy, 18 cases out of 31 cases of MQF-OK group and 9 of 30 cases of MFC group showed "improvement." According to Karnofsky's criteria 17 cases of MQF-OK group and 8 of MFC group showed effectiveness more than I-A, respectively. There was a statistical significance between the two groups (P less than 0.001). By Kaplan-Meier's method, the MQF-OK group survived longer than the MFC group (P = 0.05). The complications, such as leukocytopenia, thrombocytopenia or gastrointestinal complaints, were more frequently found in MQF-OK-432 group than in MFC group (P less than 0.05). But these complications decreased or resolved spontaneously 1 to 4 weeks after the administration of MQF-OK therapy. On these results, MQF-OK therapy was considered excellent method for treatment of inoperable gastric cancer and will be furthermore attempted against other cancers.