Renovascular hypertension (RVH) is a form of high blood pressure caused by stenosis of the renal artery, and it is an important cause of treatment-resistant hypertension and impaired renal function. The vast majority (about 90%) of RVH is caused by atherosclerotic renal artery stenosis (ARAS), followed by fibromuscular dysplasia, which is more common in younger individuals. In addition, Takayasu’s arteritis, aortic dissection, thrombosis/embolism, and various other causes can also lead to similar symptoms, but these are rare. Typically, RVH is caused by stenosis of the main renal artery trunk or major branches. Cholesterol embolism, which leads to the occlusion of numerous small arteries, can also cause hypertension, but its clinical diagnosis is difficult, and many aspects of its actual state remain unclear (refer to Chap. 15 ). Here, the focus will be on ARAS, and fibromuscular dysplasia will be discussed later.