We noninvasively evaluated the prevalence and severity of atherosclerotic lesions of the internal carotid artery in 146 nonobese, nondiabetic hypertensive patients who were free of cardiovascular symptoms. We found internal carotid artery disease in 63 patients (43%), 26 (18%) with unilateral disease and the other 37 (25%) with bilateral disease. Disease severity was correlated with age but not duration of hypertension, cholesterol level, or current smoking habit. We also followed disease progression and clinical outcome with respect to cardiovascular events for 3 years in a subgroup of 95 unselected patients. In 20 of the 93 survivors (21.5%) we noted progression of the atherosclerotic lesions that was predicted by neither risk factors nor initial status of the internal carotid artery. New neurologic symptoms developed in four survivors (4%) and symptoms of cardiac ischemia in six (6%). No survivor who developed new cerebrovascular symptoms showed progression of carotid disease. These data provide useful elements for a rational approach to prevention of the atherosclerotic complications of hypertension.