Transluminal angioplasty according to Grüntzig was performed for 10 stenoses in 7 patients with renovascular hypertension. Nine out of 10 renal artery stenoses were passable and could be dilated. Definite angiographic improvement could be shown in each case. The degree of stenosis could be decreased from 86% to 38% on average. At the narrowest point the diameter was enlarged by a factor of 3.1. The pressure gradient at the stenosis fell on average from 147 to 26 mm Hg. The maximal arterial blood pressure which was on average 254/124 mm Hg before drug treatment, and 169/97 mm Hg after high dosage antihypertensive treatment, fell to 140/84 mm Hg immediately after dilatation. Before dilatation there was a definite increase in peripheral plasma renin activity in every case which fell from 41 to 12 ng AI/ml . h. In one out of 5 patients restenosis occurred after 3 months which could again be successfully dilated. In the two younger patients blood pressure 3 to 9 months later was normal even without antihypertensives. In the older patients normal blood pressure could be maintained with mild antihypertensive treatment.