Summary— Seventy-seven patients with carcinoma of the urinary bladder were investigated by computed tomography (CT) and the results compared with those of pathological staging. The overall accuracy rate was 81 % for the estimation of local tumour extension. Perivesical tumour extension was overestimated by CT owing to previous bladder surgery or radiotherapy in about half of the cases. Nevertheless, CT gives unrivalled diagnostic information in advanced tumour invasion. The diagnostic accuracy rate of CT in the detection of lymph node metastases was 89%, compared with 73% for lymphography.