This paper discusses the role of social factors as determinants of longevity, with special focus on the oldest-old population. In ageing research, genetic and environmental—including social environment—factors are often presented as two separate, mutually independent sets of determinants. There is, however, constant interplay between genes and environment, between biological and social factors; and basically it is often impossible to distinguish between their specific impacts as determinants of longevity. Besides their “own” impact, environments, then, can be understood as contexts, or settings, for genetic influences. As far as humans are concerned, social and cultural characteristics of environments are of fundamental importance.