There is great heterogeneity in the way humans respond to medications, often requiring empirical strategies to find the appropriate drug therapy for each patient (the "art" of medicine). Over the past 50 years, there has been great progress in understanding the molecular basis of drug action and in elucidating genetic determinants of disease pathogenesis and drug response. Pharmacogenomics is the burgeoning field of investigation that aims to further elucidate the inherited nature of interindividual differences in drug disposition and effects, with the ultimate goal of providing a stronger scientific basis for selecting the optimal drug therapy and dosages for each patient. These genetic insights should also lead to mechanism-based approaches to the discovery and development of new medications. This review highlights the current status of work in this field and addresses strategies that hold promise for future advances in pharmacogenomics.