Cardiovascular disease (CVD) is the leading cause of Taiwan. L-carnitine (LC) and coenzyme Q10 is recognized as lipid soluble antioxidants. The purposes of this study are going to investigate the relation of LC and coenzyme Q10 with the markers of lipid peroxidation, antioxidant enzymes activities, and the inflammatory markers in coronary artery disease (CAD) patients. The study is designed as a three-year study. The first year is an observation study. We will recruit CAD patients who are identified by cardiac catheterization as having at least 50% stenosis of one major coronary artery, and age-gender matched healthy subjects. The concentrations of LC, coenzyme Q10, lipid peroxidation markers (TBARS and ox-LDL), antioxidant enzymes activities (catalase, glutathione peroxidase, glutathione reductase, and superoxide dismutase), and inflammatory markers are going to analysis. The second year is a single-blind, single dose intervention study. CAD subjects are recruit form the first year and randomly assigned to placebo, coenzyme Q10-150 (150 mg/d), coenzyme Q10-300 (300 mg/d), LC-1000 (1000 mg/d) or LC-2000 (2000 mg/d) groups. Intervention is going to administration for three months. Fasting blood will be obtained in each month and determine the concentration of LC, coenzyme Q10, lipid peroxidation markers, antioxidant enzymes activities, and inflammatory markers after intervention. The third year is a single-blind, multiple doses intervention study. We are going to measure the CAD subjects from the second year intervention study. After three months washout period, the subjects are assigned to placebo, coenzyme Q10-150 plus LC-1000, coenzyme Q10-150 plus LC-2000, coenzyme Q10-300 plus LC-1000, and coenzyme Q10-300 plus LC-2000 groups. Intervention is going to administration for three months. Fasting blood will be obtained in each month and determine the concentration of LC, coenzyme Q10, lipid peroxidation markers, antioxidant enzymes activities, and inflammatory markers after intervention. Hopefully, the results of this study could provide information of LC and coenzyme Q10 supplementation for clinical dietitian in advising CAD patients.