OBJECTIVES: To demonstrate a correlation between abdominal computed tomography (CT) data and the histological stage of upper urinary tract tumour (UUTT) in order to more accurately define therapeutic indications. MATERIALS AND METHODS: From 1984 to 1995, 51 patients were treated for UUTT and were assessed by preoperative abdominal CT. 41 of the 51 CT scans were considered to be interpretable and were reviewed retrospectively by a single radiologist. The CT stage and tumour diameter were compared to the pathological stage. RESULTS: CT staging had a reliability of 76%, by combining stages Ta-T2, which could not be distinguished. The sensitivity of CT to assess invasion of the renal parenchyma and ureteric or perirenal fat was 100% and 70%, respectively, with a specificity of 82% and 97%. The accuracy can be improved by decreasing the thickness of sections of the tumour. Tumour diameters (d) of pyelocaliceal tumours, measured by CT and pathology, were closely correlated (r2 = 0.83). All UUTTs less than 3 cm in diameter were found to be superficial on histology. CT correctly estimated the size of these small tumours in 14/15 cases. Overall, by setting the limit at 3 cm, CT was able to detect a superficial pyelocaliceal tumour with a specificity of 92% and a PPV of 93%; however, a CT size > or = 3 cm is not predictive of the histological stage of the lesion. CONCLUSIONS: CT is still imprecise for the staging of UUTT, as it cannot distinguish between Ta, T1 and T2 lesions, and is still not sufficiently reliable in the assessment of invasion of the periurothelial fat or of the renal parenchyma. CT measurement of the diameter of pyelocaliceal tumours can provide an argument in favour of the superficial nature of the lesion and therefore guide the therapeutic decision towards a conservative approach.