A morphological study of 200 atherosclerotic carotid sinus (CS) plaques obtained at carotid endarterectomy revealed the structural components and processes characteristic for severe atherosclerosis (foci of atheromatosis and edema, necrosis of collagen and elastic fiber, newly formed vessels and hemorrhages of various duration, lipophages and lymphocytes, portions of fibrosis and calcification, covering thinning and ulceration, thrombi, and the contents of plagues (atheromatous masses, cholesterol crystals, lipophages, calcificates) on their surface). Clinical and morphological comparisons indicated that patients with stroke had a history of signs of severer atherosclerosis than those with asymptotic CS stenosis. They were found to have more commonly vulnerable atherosclerotic plaques that showed a predominance of atheromatosis foci over the portions of fibrosis and calcification, covering thinning and destruction, formation of thrombi onto its surface. It was ascertained that concomitant arterial hypertension might play a crucial role in the pathogenesis of hemorrhages into the atherosclerotic plague.