Renal artery stenosis (RAS) is a well-recognized cause of hypertension and an important cause of progressive renal insufficiency. In renal transplant patients, RAS is also a cause of refractory hypertension and allograft dysfunction. Accurate detection and treatment of clinically relevant stenosis may cure or improve hypertension and preserve renal function. Current treatment options include medical therapy, percutaneous renal artery angioplasty with or without stent placement, or surgical revascularization.In cases of RAS, the cause in the vast majority of patients is either atherosclerosis or fibromuscular dysplasia (FMD). Atherosclerosis accounts for 70% to 90% of cases of RAS and usually involves the ostium and proximal third of the main renal artery. FMD is a collection of vascular diseases that affects the intima, media and adventitia and is responsible for 10% to 30% of cases of RAS.