Why longevity? For a number of years, the Fondation IPSEN has been devoting considerable effort to the various aspects of ageing, not only to age-related diseases such as Alzheimer's, but also to the Centenarians, the paragon of positive ageing. The logical continuation of this approach is to address the question of longevity in global terms. Behind the extreme values, what span is accessible to all of us and likely to directly concern most of our contemporaries? The individual and col lective increase in the duration of life is one of the most striking phenomena of our time. It could be one of the most significant events in the "bio-social" history of humanity. The increase in life expectancy at old age, which started a few de cades ago only, is going on. The most well-advised observer had not foreseen or even dared hope for this increase which will drastically affect our everyday life, our habits and our behavior. In the fragment of human history we are living in, it is our responsibility to deal with this major transformation for the species. Such a transformation needs an effort from all to adapt to the new conditions. This transformation has to be managed rather than simply experienced, anticip ated rather than followed, in order to avoid any attempt to pervert this major step forward. All that was present during the first symposium of the new series on longevity of the Colloques Medecine et Recherche convened by the Fondation IPSEN.