Pharmacogenomics has become a popular new field. Issues are applicable to the enzymes involved in the metabolism of “xenobiotics” (including drugs) as well as the receptors and other gene-product targets for drugs. Much is already known about the enzymes involved in xenobiotic metabolism and their genes and regulation. Programs have been implemented by pharmaceutical companies for use of these systems in screening for bioavailability and potential drug–drug interactions. New methods and pharmacogenomic approaches can be incorporated into these strategies. Toxicogenomics is a newer field that incorporates the application of pharmacogenomics principles to issues of predictive toxicity. Related to pharmacogenomics and experimental toxicogenomics are efforts to relate genomics to risk of cancer and other diseases caused by environmental chemicals and physical agents that individuals are inadvertently exposed to. The National Institute of Environmental Health Sciences has initiated the Environmental Genome Project towards this effort. Drug Dev. Res. 49:4–16, 2000. © 2000 Wiley-Liss, Inc.