Sixteen consecutive patients with renovascular hypertension were treated by transluminal dilatation and observed during 6 - 39 months (mean 21.8 months). Poststenotic renal artery pressure increased (p less than 0.001) and the renal arteries were patent on angiograms taken immediately after dilatation. In 13 patients, angiography was repeated 2 - 9 months later; at that time the selective renal vein renin ratio had decreased (p less than 0.001). At the end of the follow-up, blood pressure was improved or normal in 14 cases. One of the eight patients with atherosclerosis was normotensive without treatment, compared with five of six patients with fibromuscular dysplasia (p less than 0.05). The results in two cases with vasculitis are uncertain. The four patients with relapses, one after intimal catheter dissection, were treated successfully by redilatation. Thus, renovascular hypertension can be improved by transluminal dilatation in patients with atherosclerosis and in patients with fibromuscular dysplasia with lasting success and a low morbidity rate.