We studied the frequency of restenosis and the effects of percutaneous transluminal renal angioplasty (PTRA) on blood pressure (BP) and particularly on renal function in all patients in whom successful dilatation was performed. Restenosis was found in 42% of the patients with an atherosclerotic renal artery stenosis and in 22% of the patients with fibromuscular dysplasia. BP improvement was seen in 70–80% of the patients with unilateral stenosis or with successful bilateral dilatation (group I) whereas only seldom was an effect on BP observed in patients with more complicated disease, such as those with an occlusion of the contralateral artery (group II). Remarkably, however, both in group I and in group II, in about half of the patients an improvement in renal function was found, even 2–3 years after the procedure. Our results thus indicate that PTRA can be useful in preservation or even improvement of renal function, even if no effect on blood pressure can be expected.