Nine patients with severe renovascular hypertension underwent surgical revascularisation of their single kidney. The blood pressure normalized postoperatively in seven patients. Four of them no longer required antihypertensive medication and three required only moderate doses. One patient died of myocardial infarction three days after the operation. The ninth patient also became normotensive, but preoperative renal failure progressed and she died of cardiac failure while on haemodialysis 16 months postoperatively. The results suggest that single-kidney renovascular hypertension is more amenable to surgery than is unilateral disease in patients with two kidneys, because the hypertensive effect of the other kidney is lacking.