One hundred five patients treated with potentially curative surgery and adjuvant postoperative radiotherapy for adenocarcinoma of the rectum and rectosigmoid from 1973 through 1981 were reviewed. Radiation therapy was given with 18-25 MeV X rays in doses of 40-50 Gy in 5 weeks (midline dose) using AP-PA fields in 97 patients. A boost of 6 to 10 Gy was directed to the area of maximum risk by anterior-posterior or perineal fields in 71 patients. Local failure occurred in 15 patients and was documented pathologically in 8 patients, or clinically or radiologically in 7 patients. The local recurrences according to the Modified Astler-Coller staging criteria were: B1: 0% (0/3); B2: 4% (1/24); B3: 31% (4/13); C1: 8% (1/12); C2: 18% (8/45); C3: 20% (1/5). Local failure after adjuvant radiotherapy versus surgery alone was compared. The comparison of local failure of combined treatment versus surgery alone, from our institution, is as follows: B2-4% vs 13%, B3-31% vs 26%, C2-18% vs 30%, and C3-20% vs 49%. Sixty-one patients (58.1%) have been followed for 5 years, with a median of 73 months and a minimum of 24 months. The actuarial 5-year survival (disease-free) for the entire group is 55% and is not statistically different for the groups with negative or positive nodes. Fourteen patients (13%) required surgery for small bowel complications; four others (4%) had symptomatic small bowel obstruction treated with conservative therapy only. Small bowel obstruction occurred in 4 of 16 (25%) treated with radiation fields above L5, whereas those treated below L5 had an 11% incidence. Postoperative adjuvant radiotherapy can increase local tumor control compared to surgery alone. The small bowel complication rate in this series most likely reflects AP-PA treatment technique and can be decreased by the use of multiple fields with maximum shielding of the small intestine.