A comparative diagnostic study was carried out on 40 patients with pathologically proven renal malignancies which were staged both by angiography and CT. CT is more accurate than angiography for the detection of both perirenal and pararenal extension of the primary tumour (T-staging), and angiography is only slightly superior to CT in the evaluation of intravascular extension of the malignancy. The diagnostic performance of CT is clearly superior to angiography in detecting malignant lymphatic spread (L-staging) and distant metastases (M-staging). CT is, therefore, becoming the primary diagnostic approach for the staging of renal malignant tumours.