Fifty-seven sections of human vessels, collected in the Pathobiological Determinants of Atherosclerosis in Youth study from individuals aged 25-34, were stained with two monoclonal antibodies to oxidatively-modified lysine. Intensity and extent of immunoreactivity were graded by three pathologists. Aorta from a Watanabe heritable hyperlipidemic (WHHL) rabbit was stained as a positive control. Intimal immunoreactivity in the rabbit was predominantly localized to lesions. Although immunoreactivity in humans was somewhat more intense in atherosclerotic plaques, substantial staining was present in intima with diffuse intimal thickening and coronary veins. Localization of oxidatively-modified lysine in humans did not correlate with localization or severity of atherosclerosis. Localization of immunoreactivity for oxidatively-modified lysine to intimal lesions in the WHHL rabbit may be due to absence of diffuse intimal thickening, which prevents retention of epitopes throughout the intima. #169; 2000 Elsevier Science Ireland Ltd.