['Oxidative stress plays an important role in the pathogenesis of coronary artery disease. Recent work showed that high-density lipoproteins isolated from atherosclerotic lesions and blood of patients with established coronary artery disease contain elevated levels of nitrated apolipoprotein A-I. Methods to quantify nitrated apolipoprotein A-I in the plasma may facilitate in the determination of a correlation between plasma levels of nitrated apolipoprotein A-I and risk of atherosclerosis.', 'In this report, the presence of plasma nitrated apolipoprotein A-I in subjects with cardiovascular disease was detected by Western blot analysis and quantified by a newly developed specific sandwich enzyme-linked immunosorbent assay.', 'The precision of the assay was indicated by the good correlation obtained between enzyme-linked immunosorbent assay and Western blot (r(2)=0.96). Using these two methods, we were able to detect significant elevations (3-fold increase) of plasma nitrated apolipoprotein A-I in low high-density lipoprotein cholesterol subjects as compared to high-density lipoprotein cholesterol subjects. In addition, we found that both plasma and serum samples can be used by enzyme-linked immunosorbent assay to quantify nitrated apolipoprotein A-I concentrations. More importantly, the degree of nitrated apolipoprotein A-I-containing high-density lipoprotein particles was negatively correlated with levels of circulating apolipoprotein A-I.'] Is nitrated apolipoprotein A-I , a potential new cardiovascular marker , markedly increased in low high-density lipoprotein cholesterol subjects?