Current research suggests that loss of the vasodilator, anti-thrombotic, and anti-inflammatory properties of the vascular endothelium plays a dynamic role in the pathogenesis of cardiovascular disease. Impaired endothelial function, including impaired nitric oxide-dependent vasodilation is associated with cardiovascular disease risk factors. Further, there is growing evidence that endothelial function can be improved by risk modification. However, the available studies have not definitively resolved the issue of the cross-sectional correlates of endothelial dysfunction because they have been limited to small samples of highly selected patients. For example, it remains unclear whether hypercholesterolemia, hypertension, or elevated glucose levels are independent determinants of endothelial dysfunction. Most importantly, no study has shown a relation between endothelial dysfunction and increased cardiovascular risk. Such a demonstration would increase our understanding of the pathogenesis of cardiovascular disease and aid clinicians in identifying high risk individuals who would benefit most from intervention.