The monoclonal antibody 4E6-based ELISA was used to quantify levels of oxidized LDL in plasma. of 65 control subjects, 47 patients transplanted for dilated cardiomyopathy (DCM), and 60 patients transplanted for coronary artery disease (CAD), Levels of oxidized LDL were 0.68+/-0.039 mg/dL (mean+/-SEM), 1.27+/-0.14 mg/dL (P<.001 versus control), and 1.73+/-0.13 mg/dL (P<.001 versus control and <0.01 versus DCM), respectively. Levels of oxidized LDL were significantly lower in transplanted patients with angiographically normal coronary arteries (grade 0, 1.16+/-0.053 mg/dL; n=79) than in patients with mild (grade 1, 2.13+/-0.30 mg/dL; n=18; P<.001 versus grade 0) or severe (grade 2, 3.18+/-0.15 mg/dL; n=10; P<.001 versus grade 0 and P<.05 versus grade 1) coronary artery stenosis. Logistic regression analysis identified three parameters that were significantly and independently correlated with posttransplant CAD: plasma levels of oxidized LDL (P=.0001), length of follow-up (P=.0008), and donor age (P=.047). Thus, the present study demonstrates that plasma levels of oxidized LBL correlate with the extent of CAE) in heart transplant patients and suggests that elevated levels of oxidized LDL may be a marker for CAD.