The accuracy of various noninvasive screening tests for the detection of renal artery stenosis (urography, duplex scanning, radionuclide scintirenography, intravenous digital subtraction angiography, spiral CT and MR angiography) is discussed. All these methods may show false-negative and false-positive results. Therefore, in the case of a high index of clinical suspicion (i.e. refractory hypertension, recent elevation of serum creatinine, renal dysfunction, asymmetry of kidney size) renal arteriography must be performed. Since the natural history of atherosclerotic and fibrous renal artery stenosis is characterized by progression of the disease with loss of renal function despite good blood pressure control, surgical revascularization or percutaneous angioplasty should be performed whenever possible.