Developments in molecular biology over the past three decades have led to an increasing awareness of the importance of epigenetic phenomena in a variety of genome functions. Epigenetic aspects of complex multifactorial diseases including schizophrenia, however, have not been investigated sufficiently. Various facets of epigenetics are reevaluated through their putative relevance to four theories of schizophrenia: neurodevelopmental, dopamine dysfunction, viral, and genetic anticipation with unstable DNA. The heuristic value of the epigenetic model of schizophrenia arises from the possibility of integration of a wide variety of empirical data into a new theoretical framework. It can be hypothesized that in addition to pathological effects of DNA structural mutations and environmental factors, inherited and acquired epigenetic defects, or epimutations, may be of etiological importance in schizophrenia. In addition, the epigenetic model may lead to experiments investigating the molecular substrates of genetic-environmental interactions.