The role of heredity in modifying individual response to drugs and other chemicals has been known for more than six decades. More recently, the Human Genome Project, and various technical innovations emerging from it, have dramatically accelerated the depth of this knowledge. The collective term now given to this field is 'pharmacogenomics'. The rapid emergence of pharmacogenomics provides many exciting opportunities for achieving better health outcomes and, in particular, offers enormous potential for markedly improving drug therapy, through rational drug selection and prediction of susceptibility to adverse events or toxicity. It is envisaged that the implementation of pharmacogenomic programs will provide clinicians with greater certainty of a desired outcome, including the avoidance of underdosing, overdosing, misdosing and adverse drug reactions. Importantly, pharmacogenomics also offers the pharmaceutical industry potential economic advantages through improved drug selection and streamlined clinical trial protocols. This review provides a background to the development and conduct of pharmacogenomic research and highlights examples where pharmacogenomics is likely to have a significant clinical impact on the pharmacokinetics of drugs.