Design: prospective multicenter randomized, unblinded two-arm study. Enrolment. Eligible patients entail adult hypertensive of both genders with clinical and/or radiological evidence of unilateral or bilateral RAS. Clinical evidence of RAS will be unexplained renal dysfunction (GFR < 60 ml/min), uncontrolled or refractory hypertension (defined as resistant to lifestyle measures and to at least 3 drugs including a diuretic in adequate doses with failure in lowering systolic and diastolic BP to goal) and/or significant worsening of renal function (20% increase of serum creatinine) after administration of ACE inhibitors and/or an abdominal bruit and/or evidence of atherosclerotic involvement of other sites.