Aging is considered a risk factor in the pathogenesis of atherosclerosis. It is not clear, however, whether the relationship between aging and atherosclerosis is the result of increased susceptibility of the arterial wall related to intrinsic alterations or the expression of the increase in intensity or duration of exposure to risk factors. In this study, we used aged (median age 46 months) and young (4 months old) New Zealand white rabbits. Nine aged and 11 young rabbits received a hyperlipemic diet enriched with a low dose of cholesterol for 18 months. Eleven aged and 8 young rabbits, fed standard chow for the same period, were used as controls. Using morphologic and morphometric methods, we detected in aged hyperlipemic rabbits (a) a marked prevalence of fibroatheromatous plaques (as opposed to fatty streaks in young hyperlipemic rabbits); (b) aortic lesions more extensive and of greater dimensions than in young hyperlipemic rabbits; (c) fibroatheromatous plaques in carotids and raised fatty streaks in the large subepicardial coronary branches. Our results show an increased susceptibility of the aged arterial wall to hypercholesterolemia.