In patients with severe hypertension a search for a renal cause, particularly for a renal artery stenosis, needs to be undertaken with 24-hour blood pressure measurement, urinary examination, determination of renal function and duplex sonography of the kidneys.--Sympathetic hyperactivity, which is associated with an increased cardiovascular risk, may already be found in an early stage of renal diseases. There is evidence that administration of an ACE inhibitor or an angiotensin receptor antagonist (ARB) may induce a decrease of sympathetic hyperactivity as well as a reduced rate of adverse cardiovascular events in patients in renal failure.--In patients with renal disease and high proteinuria antihypertensive therapy with ACE-inhibitors or ARB delays the progression of chronic renal failure. Combined therapy of ACE-inhibitors plus ARB may reduce proteinuria more than that would be the case with either of these drugs alone. However, there is no evidence that combination of these two drugs improves renal function more than monotherapy.--Renal artery stenosis of > 70% should be treated by dilatation, if there is evidence of fibromuscular dysplasia. Dilatation and/or stent implantation in an atherosclerotic renal artery stenosis of > 70% should be performed if indicated by the patient's clinical state. i.e. severe hypertension has proved to be resistant to triple drug antihypertensive therapy or pulmonary edema has occurred frequently. Preservation of renal function by angioplasty of an atherosclerotic renal artery stenosis remains a challenge. However, exact criteria for such intervention need to be established. But so far there have not been adequate data from controlled prospective trials.