The most frequent obstructive lesions of renal arteries are atherosclerotic stenoses. Owing to methodological biases, it is difficult to know the exact prevalence of atherosclerotic stenosis. It increases with other manifestations of generalized atherosclerosis and aging. Renal artery thrombosis and embolism are also frequent and may occur as a complication of arterial catheterization. Atherosclerotic renal stenosis and embolism are now a common cause of renal failure. Fibrous dysplasias are the second cause of renal artery stenosis. Medial fibroplasia is the most common form, accounting for 75-80% of the total number. Other less common renal artery diseases are Takayasu's disease, congenital abnormalities, and the complications of radiotherapy.