Sixty patients with bladder carcinoma were examined by CT prior to radical cystectomy. CT indicated perivesical tumour growth or extension to neighbouring organs correctly in 68% of these cases. Overstaging was observed in 23% and understaging in 8% of the cases. Most of the difficulties concerned assessment of tumours in the anterior bladder wall and identification of the plane between the bladder and the seminal vesicle. In most instances CT provided no supplementary information to clinical staging, but was useful when obesity or previous irradiation impeded clinical staging.