This retrospective study reviews the outcome of patients with Dukes' B and C rectal cancer treated with adjuvant post-operative pelvic radiotherapy at the Peter MacCallum Cancer Institute from 1981 to 1990. Sixty-one patients (22 Dukes' B, 36 Dukes' C and 3 unknown stage) received a median dose of 50 Gy of pelvic irradiation. Locoregional relapse occurred in 33% of patients. Estimated median progression-free survival was 1.7 years with 46% surviving without progression at 2 years and 30% at 5 years. There was no difference according to Dukes' stage. The estimated median survival was 2.6 years, with no difference according to disease stage. These results with postoperative radiotherapy alone are inferior to results achievable by combination chemotherapy and radiotherapy as adjuvant therapy which should now be considered standard therapy following surgical resection for Dukes' B and C rectal cancer.