The structure of arteries changes with age. Gradual disappearance of elastic fibres facilitates dilatation of the arterial lumen and increase in length of the vessels. Simultaneously, the arterial wall becomes thicker, but it is often difficult to distinguish the changes due to ageing from those caused by atherosclerosis. These structural alterations result in a greater rigidity of the arteries, which can now be evaluated by non-invasive segmental methods. This shows that ageing does not have the same functional effects on wide-caliber elastic arteries and on middle-sized muscular arteries. The increase of systolic arterial pressure observed in the elderly is a consequence of structural and functional changes in the arterial system.