Hypertension is a common complication observed after renal transplantation. If the hypertension is of renovascular origin, transluminal angioplasty or surgery of the renal artery stenosis can lead help cure the hypertension. The blood pressure of a 31-year-old man who underwent renal transplantation 2 years earlier gradually increased. Arteriography showed stenosis (>80%) in the two branches of the renal artery. To help confirm the presence of renovascular hypertension, captopril renography was performed but showed no significant changes compared with baseline renography. Renography was performed again after losartan administration and showed impaired renal function. In this case, losartan renography was more useful than captopril in suggesting renovascular hypertension.