One hundred and twenty-five patients, previously operated for rectal or rectosigmoid cancer, have been submitted to external radiation therapy from 1964 to 1985 on pelvic and/or perineal recurrence (50 perineal, 66 pelvic, 9 both). Fifty-seven per cent received more than 50 Gy, but only 14% more than 60 Gy. Overall survival has been poor (66% at 1 year, 20% at 3 years, 15% at 5 years) whereas better results have been achieved for pain relief: complete remission in 49% and partial remission in 26% of 77 symptomatic patients. Among 94 patients, evaluable for tumor size before and after treatment, radiation significantly decreased the size of the recurrence in 63% (27% CR). Among prognostic factors (recurrence site, radiation dose, age, pain relief and disease-free interval since surgery) only perineal recurrence without pelvic involvement, if treated with high doses (greater than 50 Gy), seems to be related to a significantly improved prognosis.