From 1970-1981, 85 patients had curative sigmoid resections for adenocarcinoma and were eligible for postoperative adjuvant therapy. In a nonrandomized fashion, 10/28 B2,3 and 7/28 C2,3 patients received postoperative pelvic radiation therapy (4500-5100 rad/5-6 weeks). Compared to the 39 B2,3 or C2,3 patients not receiving adjuvant pelvic irradiation, those 17 who did demonstrated retrospectively an improved pelvic regional disease control rate (70 versus 91%) and an improved five-year survival for irradiated B2,3 cases versus unirradiated B2,3 cases. (100 versus 64%, P less than 0.05). C2,3 cases showed no survival advantage for pelvic irradiation. This retrospective analysis suggests that for sigmoid carcinoma patients, postoperative adjuvant pelvic irradiation may be beneficial in terms of improved regional disease control rates for B2,3 and C2,3 cases and also improved survival for B2,3 cases.