 The vascular endothelium inner lining of cells in blood vessels normally prevents vasospasm and thrombosis by producing nitric oxide and other regulatory substances. In patients with atherosclerosis, endothelial function is impaired. Excess production of reactive oxygen species free radicals contribute to endothelial dysfunction in atherosclerosis, and some prior studies have shown a beneficial effect of antioxidant treatment on endothelial function in patients with coronary artery disease. On the other hand, reactive oxygen species may be required for normal endothelial function and antioxidant supplements failed to show a benefit in large clinical trials. The effect of antioxidant treatment on endothelial function in healthy subjects is unknown. The present study will test the hypothesis that scavenging reactive species might reduce endothelium-dependent vasodilation in healthy subjects. 