INTRINSIC AND EXTRINSIC FACTORS: Skin ageing is due to the conjunction of intrinsic (chronological ageing) and extrinsic factors (fundamentally photo-ageing). The physiopathological mechanisms of intrinsic ageing rejoin those of the ageing of all the other organs. Among the intrinsic causes, tobacco and above all ultra-violet radiation, UVB and also UVA, play a preponderant role. Photo-ageing is secondary to complex mechanisms that are increasingly known. The UVB directly interact with the DNA of the cutaneous cells. The deleterious effects of UVA are principally due to the formation of free radical oxygen, which result in an alteration in the nuclear and also mitochondrial DNA, but also an activation of the enzymes, metalloproteinase, capable of damaging the extra-cellular matrix. DELETERIOUS CONSEQUENCES: The phenomena of ageing provoke the decline in defence, healing and perception mechanisms and in the thermoregulation of the skin tissue. There are numerous and often unsightly clinical manifestations. Photo-ageing can be considered as a marker of risk of photo-carcinogenesis requiring increased clinical surveillance. PREVENTIVE AND CURATIVE MEASURES: The prevention of skin ageing must be based on the use of sunscreens protecting against both UVB and UVA, but, in order for them to be effective, they require a change in general life style. There are many efficient therapeutic means, but the possible side effects must be known and explained to the patient. Retinoids, in view of their innocuousness and efficacy not only in prevention but also treatment of skin ageing, should be considered as a therapeutic option of choice.