The goal of this chapter is to demonstrate the importance of incorporating gene by environment (GxE) interactions into behavioral science theory and research. In pursuit of this aim, the chapter is organized in the following way. First, we provide a brief critique of the behavioral genetics paradigm, noting why one should be skeptical of its suggestion that genes exert large main effects, and only main effects, on social behavior. Second, we describe how the recent mapping of the human genome has facilitated molecular genetic research and the emergence of the new epigenetic paradigm that has begun to supplement and replace the simpler model of genetic determinism. Third, we turn our focus to the explosion of GxE research that has occurred in the wake of this paradigmatic shift. These studies find that genetic variation often interacts with environmental context to influence the probability of various behaviors. Importantly, in many, and perhaps most, of these studies the genetic variable, unlike the environmental variable, has little if any main effect on the outcome of interest. Rather, the influence of the genetic variable is limited to its moderation of the effect of the environmental construct. Such research does not undermine the importance of environmental factors; rather it shows how social scientific explanations of human behavior might be made more precise by incorporating genetic information. Finally, we consider various models of gene - environment interplay, paying particular attention to the differential susceptibility to context perspective. This model of GxE posits that a substantial proportion of the population is genetically predisposed to be more susceptible than others to environment influence. We argue that this model of GxE is particularly relevant to sociologists and psychologists.