A 64-year-old man with a unilateral 15 mm diameter renal cell carcinoma underwent percutaneous radiofrequency ablation (RFA) assisted by CT during renal arteriography (angio-CT). Prior to placement of the needle electrode, a 5 Fr angio-catheter was placed in the right renal artery, and angio-CT was performed before, during and after the procedure. Since multiple angio-CT can be performed using a small amount of diluted contrast agent, RFA can be monitored without impairing renal function. As a result, this imaging combination was found to be useful for determining the end point of ablation.