Recent research suggests that the social environment can moderate the expression of genetic influences on health and that genetic influences can shape an individual’s sensitivity to the social environment. Evidence supports four major mechanisms: genes can influence an individual’s response to stress in the environment, genes may enhance an individual’s sensitivity to both favorable and adverse environments, inherited characteristics may better fit with some environments than with others, and inherited capabilities may only become manifest in challenging or responsive environments. Further progress depends on better recognition of patterns of interaction between genes and the environment, improved methods of assessing the environment and its impact on genetic mechanisms, the use of appropriately designed laboratory studies, identification of heritable differences in receptor or effector systems before environmental moderation occurs, and clarification of the timing of the impact of social and genetic moderation.