Many young adult subjects have some degree of atherosclerotic coronary and carotid artery disease and experience no symptoms. As time passes, many die suddenly and unexpectedly and only limited therapeutic process begins in youth, a measure of the early manifestations of atherosclerosis may have the potential of identifying subjects at risk for premature coronary and carotid occlusive vascular disease when therapeutic options can be administered. Impaired brachial artery flow mediated dilatory (FMD) capacities have been shown to exist in children and young adults with hypercholesterolemia, hyperhomocysteinemia, diabetes and in those who smoke. Impaired brachial artery FMD has been shown to related to impaired endothelial function, which is an early manifestation of the atherosclerotic process. If impaired brachial artery FMD is a predictor of the process, then it may be used to non-invasively assess atherosclerosis early in its development and to evaluate the effect of therapeutic interventions.