A 26-year-old woman with neurofibromatosis 1 was admitted to our hospital for investigation of prolonged hypertension after toxemia of pregnancy. Plasma renin activity was elevated. From the renogram, stenosis of right renal artery was suspected and we performed renal arteriography, which revealed proximal right renal artery stenosis. The intravascular ultrasound (IVUS) image showed concentric stenosis with intimal and medial hypertrophy, which was iso-echoic and partly high echoic. Percutaneous transluminal renal angioplasty was performed and the lesion was well dilated. After angioplasty, blood pressure normalized in a week. From the clinical course and the IVUS image, we suspected that renal artery stenosis was due to neurofibromatosis 1.