Computed tomography of the pelvis has been performed in 60 patients with epithelial bladder tumours. The CT findings have been compared with the clinical staging (T-stage), lymphography (N-stage) and wherever possible the surgical staging (P-stage). Although the intraluminal tumour was visualised in a high proportion of examinations, the greatest value of CT is in the accurate delineation of the extravesical extension of the growth. This is likely to be the primary role of CT in the staging of bladder cancer. Difficulties in detecting invasion of contiguous organs, particularly the prostate, and the failure to demonstrate nodal involvement within the pelvis were noted. The technique has clear advantages over more invasive investigations and the additional information provided over and above clinical staging is seen as a major advance in the assessment of these tumours.