A 78-year-old man had a tumor of Borrmann type II affecting about one third the circumference of sigmoid colon, which was diagnosed as well-differentiated adenocarcinoma from biopsy. Although surgical intervention was recommended and the radical operation seemed possible from preoperative examination, the patient first refused it. Of necessity, systemic administration (s.c) and single endoscopic topical infusion of OK-432 and oral treatment of UFT were performed for 1 month. Since the patient agreed to receive an operation later, sigmoidectomy and lymph node dissection (R 2) were performed, resulting in the disappearance of tumor cells histologically. One week before endoscopic infusion, oral UFT and subcutaneous OK-432 were initiated. Although no macroscopic change was found during the topical infusion as compared with the time of first examination, the bulging disappeared, showing a polypoid change and IIc-like findings after 3 weeks. The operation was performed after an additional week, after which a benign tumor was found macroscopically and the disappearance of tumor cells histologically. Although many reports have dealt with the effect of endoscopic treatment for gastric carcinoma, there have been fewer reports describing the endoscopic treatment performed in patients with colon carcinoma, making it difficult to evaluate its therapeutic effect. However, this endoscopic therapy was suggested to be capable of becoming a useful treatment for inoperable colon carcinoma from the present case, whereas chemotherapy was found to have almost no effect on colon carcinoma in general.