The endothelium is the first line of tissue whose function is affected by the cardiovascular risk factors. The normal function of this vascular covering maintains the homeostasis of the vascular bed and its alterations favors the appearance of the initial lesions of various diseases including the atherosclerotic process. The endothelial function can be measured by means of non invasive methods and these measures can identify the people at higher risk to develop atherosclerosis and its complications and also the methodology has proven to be useful in the evaluation of the outcomes related to the therapeutic measures. The possibility of performing this methods in a safe, non invasive and reproducible way permits that the endothelial function could be used as screening tool for cardiovascular risk in open population.