This article proposes an interactional model in which individuals may actively seek suitable environments. Rejecting either a hereditarian or an environmentalist emphasis, this approach recognizes that both genetic endowment and social background determine the mobility of the individual. The article treats the following five topics: the basic biosocial assumptions underlying the interaction model; the operation of self-selection as an integral part of this model; the capacity of individuals to envision alternative environments; an examination of three basic genotype-environment interactions; the political ramifications of these interactions both on an individual and on a societal level.