The recently completed sequencing of the human genome heralds a new era in the study of social influences upon health. Because the interactions between genes and the environment are bidirectional, expertise in the areas of psychosocial processes and health behaviors will be necessary for elucidating how genes, behavior, and the environment interact to affect health outcomes. For investigators whose primary background is in social health research, the terminology used by geneticists may seem like a foreign language. To help navigate this foreign territory, the nature of genetic variation and gene action is presented in non-technical terms using the serotonin transporter gene as an example because it is thought to influence sensitivity to the social environment. In addition, we describe several methodological pitfalls to be avoided when associating genetic variation with psychosocial and behavioral risk factors for poor health outcomes.