Ninety-seven patients with adenocarcinoma of the rectosigmoid have been treated with high dose (5000-6000 rad) preoperative irradiation from 1960 through 1972 at the University of Oregon Health Sciences Center. Fifty-seven were initially clinically resectable and 40 were initially inoperable. Forty of the 57 initially clinically resectable patients had "curative" resections and are at risk for more than 5 years. An increase in 5-year survival (from 38% to 53%) and an absence of pelvic recurrence have occurred in those patients receiving preoperative irradiation and "curative" resection. Four of the 40 initially inoperable patients are alive without tumor. Three of the four survivors had irradiation and surgery; one had irradiation only. An additional four patients had no evidence of tumor at death. Tumor was totally sterilized by irradiation and nine patients and reduced to microfocal extent in an additional three of the 97 patients. Incidence of complications was no greater than has been reported in a surgical series from the same institution.