OBJECTIVE: To compare the findings of multidetector computed tomography (CT) with surgical pathology and magnetic resonance imaging (MRI), to determine the accuracy of delineating the superior extent of inferior vena cava (IVC) thrombotic involvement in renal cell cancer (RCC). PATIENTS AND METHODS: A prospective database was examined of 11 patients (median age 65 years, range 45-77) being assessed for suspected IVC extension of RCC tumour thrombus with both multidetector CT and MRI. All had pathology confirming RCC, and eight of those undergoing surgery had pathological confirmation of tumour thrombus extent. All images were analysed originally, then re-analysed by two independent radiologists, an experienced urologist and a urological trainee unaware of the original reports and other imaging results, with a final determination on tumour thrombus level by consensus. RESULTS: The multidetector CT results were completely accurate when compared with surgical specimens and were in agreement with MRI on all but one occasion, where MRI determined the renal vein to be clear when it was involved on CT and at surgery, giving MRI an accuracy of seven of eight samples. CONCLUSIONS: Whilst there were few patients and further studies are needed, multidetector CT was comparable with MRI in determining tumour thrombus level. More importantly, in the eight patients with surgical pathological confirmation, multidetector CT was accurate in all. Ultimately, it may replace MRI as the 'gold standard' for imaging to delineate the upper limit of tumour thrombosis in RCC.