Between 1950 and 1983, radiation-induced proctitis was diagnosed proctoscopically in 720 patients at the Mayo Clinic. Sixty-two patients with severe colorectal symptoms were treated surgically. The interval from cessation of radiotherapy to onset of symptoms ranged from 3 weeks to 24 months (mean 33 months). The 62 patients underwent a total of 143 operations with 8 operative deaths (13 percent), and 40 patients (65 percent) had 61 complications. The morbidity rate was lower after colostomy alone (44 percent in 27 patients) than after more aggressive operations (80 percent in 35 patients). Transverse loop colostomy and descending colostomy were safer than sigmoid colostomy. The dissection adhesions, opening of tissue planes, and careless manipulation of intestine may result in necrosis and perforation of the intestine, bladder, or vaginal wall; these were the main causes of fecal and other internal fistulas in our study.