This synthesis of the literature on radiotherapy for rectal cancer is based on 73 scientific articles, including 1 meta-analysis, 32 randomized studies, 22 prospective studies, and 1 retrospective study. These studies involve 15042 patients. The reviewed studies show that adjuvant radiotherapy for operable rectal cancer can reduce the risk for local recurrence. A meta-analysis of 11 randomized studies reported a 25% risk reduction. The same meta-analysis suggests that adjuvant radiotherapy can reduce mortality by 10%, but this has not been statistically confirmed. The clinical effects of radiotherapy may depend on when it is given in relation to surgery. The issue of preoperative or postoperative radiotherapy is being investigated in several prospective randomized studies. Fractionation, administration of anticancer drugs during radiotherapy, and surgical methods, including associated radicality, also appear to be of importance. Local recurrence of rectal cancer is accompanied by severe suffering for the patient, eg, severe pain that is difficult to control by medication and surgery. Hence, there are major benefits from avoiding local recurrence. Given current knowledge, radiotherapy (preferably preoperative) is indicated in conjunction with operable rectal cancer, mainly Dukes' group C. External radiotherapy provides valuable palliation in many patients with locally advanced rectal cancer. In isolated cases, treatment appears to lead to prolonged disease-free survival, mainly in patients with local recurrence who have not already received pre- or postoperative radiotherapy. Experiences from different models of combination therapy involving chemotherapy and intraoperative radiotherapy are too limited to permit reliable conclusions: mainly since observation times are relatively short.