For patients with resectable rectal cancer treated with total mesorectal excision, the routine use of radiotherapy should be omitted for stage I of the disease and for lesions located higher than 10 cm from the anal verge. Preoperative radiotherapy may be considered for all patients with a lesion with deep perirectal fat infiltration located in the lower two thirds of the rectum. The other option is to offer postoperative radiotherapy for patients with a positive surgical margin, N+ stage disease, mesorectal tumour implants, high tumour grade, perineural invasion, extramuscular blood and lymphatic vessel invasion and with inadvertent tumour perforation. The lower risk of small bowel damage and probable higher efficacy are arguments for the use of preoperative radiotherapy instead of postoperative radiotherapy. The impairment of anorectal function appears to be most frequent late postirradiation sequel. The analysis of acute complications (including toxic deaths) compliance, cost and convenience favours 5 x 5 Gy preoperative irradiation with immediate surgery for patients with resectable tumours in comparison to other commonly used schemes of radiotherapy. These advantages should be weighed against approximately 1.5% risk of late neurotoxicity. There is no clear answer to the question whether preoperative conventional radio(chemo)therapy offers an advantage in sphincter preservation. To answer this question, the results of two ongoing randomised trials are awaited. For patients with unresectable cancers, long-term preoperative radio(chemo)therapy with delayed surgery is a preferable scheme. The total mesorectal irradiation should be employed for mid- and low-lying lesions. Therefore, during radiotherapy planning, a contrast enema should be used to identify the anorectal ring, anatomically corresponding with the lowest edge of the mesorectum.