Endothelium plays a primary role in modulating vascular tone and structure through production of the relaxing factor nitric oxide (NO), which also protects the vessel wall against the pathogenesis of atherosclerosis and thrombosis. A dysfunctioning endothelium due to reduced NO availability and increased production of oxidative stress is considered an early indicator of atherothrombotic damage and of cardiovascular events. Aging is associated with the development of cardiovascular structural and functional alterations, which can explain the age-related increase in cardiovascular risk. Advancing age is associated with endothelial dysfunction in both normotensive subjects and essential hypertensive patients, an alteration caused by a progressive impairment of the NO pathway and production of oxidative stress. Once oxidative stress production becomes detectable, NO availability is totally compromised. Essential hypertension represents a mere acceleration of the changes induced by aging on endothelial function. Currently, dynamic physical activity represents the only effective intervention in preventing age-related impaired endothelium-dependent vasodilation in aged healthy individuals.