Atherosclerosis is the most common cause of renovascular hypertension secondary to hemodynamically significant stenoses (> 60% diameter reduction). To assess the prevalence of atherosclerosis in the peripheral arteries and carotid bifurcation, we prospectively studied 60 patients who had renal artery stenosis documented by ultrasonic duplex scanning. Disease of the peripheral arterial circulation was assessed by the measurement of the ankle/brachial systolic pressure ratio. To evaluate the extracranial carotid artery, ultrasonic duplex scanning was employed. The prevalence of a 50-100% diameter reducing stenosis in the carotid artery was 46% in patients with a > 60% diameter reducing renal artery stenosis. The prevalence of severe peripheral arterial disease was 73% in those patients with a high grade renal artery lesion. The prevalence of severe disease in the peripheral and carotid arteries was less (50% and 25%, respectively) in patients with renal artery lesions that reduced the diameter of the renal artery less than 60%. The high prevalence of associated lesions in the carotid and peripheral circulation in patients with renovascular disease secondary to atherosclerosis should prompt investigation of these major arteries when renal artery disease is detected. Disease of the carotid and peripheral arteries is a common cause of morbidity and should be treated according to accepted guidelines.