The treatment of rectum cancer depends on the tumour stage, and until 2005 treatment included preoperative radiation therapy for the T3 and T4 cancer stages. An exact preoperative assessment of the cancer stage is therefore essential. In Denmark rectal Magnetic Resonance Imaging (MRI) is used as a standard procedure in preoperative evaluation, sometimes supplemented by transrectal ultrasound (TRUS). The purpose of this study was to determine the accuracy of preoperative MRI in tumour stage evaluation in order to correctly select the patients who will benefit from preoperative radiation therapy.