['Matrix metalloproteinases are involved in atherosclerosis and plaque vulnerability.', 'To investigate serum levels and genetic polymorphisms of matrix metalloproteinases (MMPs) -1, -3 and -9 in patients submitted to carotid endarterectomy.', 'Genetic polymorphisms were evaluated using polymerase chain reaction (PCR-RFLP); serum levels were measured using ELISA; histological sections were stained with Picrosirius Red to analyze the fibrous cap thickness, lipid core and collagen content and with hematoxylin--eosin to detect the presence of intraplaque hemorrhage.', 'MMP-9 serum levels were significantly higher in patients with a thinner fibrous cap (p\u2009=\u20090.033) or acute or recent intraplaque hemorrhage (p\u2009=\u20090.008) on histology, as well as in patients with previous stroke (p\u2009=\u20090.009) or peripheral vascular disease (p\u2009=\u20090.049). No consistent associations were observed between different MMP genotypes and fibrous cap thickness, lipid core, collagen content or intraplaque hemorrhage.'] Are serum levels and polymorphisms of matrix metalloproteinases ( MMPs ) in carotid artery atherosclerosis : higher MMP-9 levels associated with plaque vulnerability?