Renovascular hypertension and high renin hypertension were found to be associated with an excess prevalence of carotid artery atherosclerotic lesions and to a higher risk of stroke, respectively, as compared to low-to-normal renin hypertension. Primary aldosteronism, being characterized by hypertension and a chronically suppressed plasma renin activity, should be accompanied by a low prevalence of carotid artery lesions. To verify this hypothesis we investigated prospectively, by a high resolution duplex ultrasound technique, the prevalence of extracranial carotid artery lesions in a case-controlled study of 34 (22 women and 12 men, aged 22 to 76 years) patients with no history or symptoms of cerebrovascular disease. Primary aldosteronism was diagnosed in 17 patients; 12 had a surgically confirmed unilateral aldosterone-secreting adenoma; and 5 had idiopathic hyperaldosteronism. Each primary aldosteronism patient was individually matched with a control with primary hypertension for sex, race, age, body mass index, casual blood pressure levels, duration of hypertension, smoking, diabetes mellitus, total serum cholesterol, and triglycerides. After the matching, the two groups were similar in terms of demographic features and overall cardiovascular risk profile (all P = NS). However, plasma renin activity and aldosterone levels were significantly lower and higher, respectively, in primary aldosteronism than in primary hypertensive patients. In primary aldosteronism the overall prevalence of carotid artery lesions at duplex was 59%, not significantly different from that (53%) found in primary hypertensives. Thus, at variance with renovascular hypertension, primary aldosteronism is not associated with an excess prevalence of carotid artery lesions.