Intravascular ultrasound (IVUS) is a new tomographic imaging method suitable for evaluating vascular-wall morphology. Accordingly, there is not yet sufficient data on results obtained with IVUS in cases of renovascular hypertension. Recognizing the need for more data, we assessed the effect of balloon angioplasty in two cases of renovascular hypertension. IVUS examination of these patients demonstrated thickened sonolucent zones at the site of angiographic stenosis. These thickened sonolucent zones were thought to represent medial fibromuscular hyperplasia. Improvement in the luminal area after balloon angioplasty in both cases was assumed to be associated with intimal and medial disruption. IVUS provides detailed images of abnormal wall morphology not obtainable with angiography in patients with renovascular hypertension.