This paper is a short overview of the role of radiotherapy alone to locally control rectal cancer when surgery for any reason cannot be performed. High dose irradiation is necessary using endocavitary (contact X-ray, iridium brachytheraphy) techniques. For T2-3 lesions a combination of external beam radiotherapy and endocavitary irradiation can provide long term cure with limited toxicity. Surgery remains, by far, the main treatment of rectal cancer, preoperative radiotherapy may be used in low rectal cancer to improve the chance of sphincter saving procedure.