Recent revolutionary changes in molecular biology have spawned the disciplines of genomics and proteomics that systematically generate and analyze the information about genomes, gene transcripts, proteins and their functions in a global, comprehensive manner. The applications of these approaches present tremendous opportunities in almost every aspect of bioscience research. One such opportunity concerns selenium, an essential trace element for humans and many other forms of life, which has been associated with reduced cancer risk. Interestingly, the biological activities of selenium as a nutrient, a cancer preventive agent, or even a toxicant, are dependent on the dose and the chemical form of the element. However, the molecular mechanisms by which selenium exerts these effects largely remain unknown. This article outlines the current status of genomic and proteomic techniques and their application in selenium research, particularly as it relates to the prevention of tumorigenesis.