One hundred patients with inoperable, unresectable, or recurrent adenocarcinoma of the rectum were stratified and randomized to WR-2721 plus radiation therapy (WR + RT) or radiation therapy (RT) only treatment arms. The protector, WR-2721, was administered at a dose of 340 mg/m2 15 minutes before RT, 4 days a week for 5 weeks. The entire pelvis received 225 cGy per fraction for a total of 4500 cGy. The RT only group received the same treatment schedule. After this, both groups received a conedown of 720 cGy in 4 fractions. Inoperable and unresectable cases received a second conedown of 720 cGy. No moderate or severe pelvic normal tissue late effects were seen in the 34 evaluable patients in the combination group. However, in the RT only group, 5 of 37 evaluable patients exhibited late effects of moderate or severe degree. This difference was statistically significant (P = 0.03). There was no evidence of tumor protection by WR-2721. Sixteen percent of patients randomized to the WR + RT group had a complete response compared with 10% in the RT only group. The conditions of 12 patients of 100 became operable and 8 were resected. Seven of these patients remain free of recurrence.