Endothelial dysfunction is present in patients with atherosclerosis, even in the early stages of disease, before plaque formation. Thus, it is a useful marker for early cardiovascular disease. In recent studies, statin therapy has been shown to improve endothelial function by increasing production of nitric oxide, a key vasodilator, from the endothelium. The improvement in endothelial function occurs by lipid lowering as well as by nonlipid mechanisms. These effects begin early in treatment, supporting prompt initiation of statin therapy. The functional benefits that result from an improvement in endothelial dysfunction include enhanced myocardial perfusion, reduced duration and burden of transient myocardial ischemia, and reduced angina pectoris. As dysfunctional endothelium encourages the recruitment of leukocytes into the arterial wall and thereby predisposes to inflammation and plaque disruption, improvement in endothelial function leads to plaque stabilization.