Over the past two decades, the applications of genetic and genomic technologies have begun to transform research questions and practices within epidemiology and toxicology, the "core sciences" of public health (Annu. Rev. Public Health 21 (2000) 1). These technologies provide new models and techniques for studying genetic traits, environmental exposures, and gene-environment interaction in the production of human health and illness. This paper explores the consequences of emergent genetic and genomic approaches, their ongoing redefinitions of both genetic and environmental "risks", and their potential implications for public health practice. The central argument of the paper is that the increasing focus on gene-environment interaction directs scientific, biomedical, and public health attention both inward, to the gene/genome, and outward, to particular places. In so doing, studies of gene-environment interaction create a challenging and productive tension-at the same time that bodies are being geneticized (Am. J. Law Med. 17 (1992) 15), they also are emphatically emplaced, located where social and cultural practices come to matter. This tension, this simultaneous movement outward and inward, towards the gene and towards the environment, into the body and into place, opens up a vista into the processes through which culture and biology form a locally and historically situated dialectic (Encounters With Aging: Mythologies of Menopause in Japan and North America, University of California Press, Berkeley, CA, 1993) and raises important questions about the production of health and illness.