AbstractFifty-two patients with carcinoma of the rectum underwent computed tomography (CT) in the immediate preoperative period. CT was used in order to assess extrarectal tumour spread. The resected specimen was staged by the pathologist who subdivided spread in continuity beyond the bowel wall into slight, moderate or extensive. In 21 out of 23 patients with no or slight extrarectal local spread CT showed normal perirectal fat. Extrarectal spread was demonstrated by CT in eight of the nine patients found to have extensive local spread. This was seen to be circumferential in the only two patients with inoperable tumours. CT identified discrete nodal enlargement in seven of the 18 patients with histologically involved lymph nodes. CT may help the less experienced surgeon, especially when he is not confident of his findings at digital examination. CT allows assessment of high rectal tumours which cannot be examined digitally. It may play a role where a tumour with extensive local spread is clinically suspected and confirmation is needed before preoperative radiotherapy is given.