We have recently found that adducts of lipids, particularly cholesterol, with apolipoprotein B (apoB) are stable markers of human plasma low density lipoprotein (LDL) oxidation [7]. In this study we attempt to assess the relationship between the degree of plasma LDL oxidation, evaluated by the content of apoB-bound cholesterol and the ability of LDL to induce cholesterol accumulation in cultured human aortic intima smooth muscle cells, i.e., LDL atherogenic potential. LDL samples of 32 out of 39 healthy subjects did not increase cholesterol content in cells cultured from grossly normal intima of human aorta. Most of LDL preparations isolated from coronary atherosclerosis patients with (34 out of 43) or without (35 out of 45) hypercholesterolemia stimulated intracellular cholesterol accumulation by 32-302%. The ability of human LDL to induce cholesterol accumulation in aortic smooth muscle cells did not correlate with the degree of in vivo LDL oxidation (r = 0.10, n = 127). These results suggest that atherogenicity of LDL circulating in human plasma does not depend on the degree of lipid peroxidation in LDL particles.