This chapter considers how genes might interact with aspects of the social environment in the genesis of psychiatric disorders. Psychiatric research has been revolutionised by molecular genetics, such as the hunt for candidate genes for schizophrenia. The search for gene-environment interactions depends crucially on the development of similarly sophisticated means of measuring environmental risk. The chapter describes evidence for such interactions from early adoption studies to recent investigations using modern molecular genetic techniques. It discusses the principal methodological issues of such research, and the need for clarification of the mechanisms of gene-environment interaction. Differences in environmental and phenotypic measures are understandable given that many gene-environment studies will necessarily be opportunistic, taking advantage of large datasets such as birth cohorts where much of the phenotypic and environmental exposure data have been collected. Finally, the chapter also considers the challenges that increasing knowledge of epigenetics will bring to the field.