The records of 88 patients with radiation-induced proctosigmoidosis seen over an 8 yr period were reviewed. Of these, 84 (95%) had been irradiated for a gynecological malignancy. The peak incidence of bleeding occurred after a latent period of 9 mo. from the time of irradiation. Subjects (25; 28%) had associated injury to the urinary tract. A wide spectrum of radiological abnormalities found on barium enema is described. Patients (24; 27%) underwent operations for radiation-induced injury to the colon and urinary tract. Operations on the bowel were attended by a high complication rate (79%). A clinical classification based on bowel symptoms is presented. Those whose only symptom was low grade rectal bleeding (Group I) had the most favorable outcome and, of these, 35% stopped bleeding spontaneously by 6 mo. Patients who required frequent transfusions (Group II) had an increasing mortality rate with the passage of time. Patients whose predominant symptoms were pain and bowel dysfunction (Group III) had the highest death rate but some did well after an operative procedure.