The promise of medical care in the 21st century is that of 'personalized medicine'. Using the tool of pharmacogenetics, physicians may soon be able to choose drugs and dosages tailored toward specific patients based on their genetic profile and the genetic basis of their disease. To reach this goal, pharmacogenetics needs to be better incorporated into clinical research and drug development. Historically, pharmacogenetic research has been restricted to the search for polymorphisms in one or several genes thought to be involved in a drug's disposition. However, this 'candidate gene' approach has limited pharmacogenetic discoveries. As the understanding of drug metabolism has increased, including the appreciation that drugs pass through complex metabolic pathways rather than experience a single enzymatic modification, it has become clear that pharmacogenetic research must expand beyond the candidate gene approach. Genomic microarray technology posits a solution to this need to expand clinical research applications. A new tool developed by Affymetrix Inc, termed DMET (drug metabolism enzymes and transporters) Plus, can genotype 1936 variations in 225 genes involved in drug disposition. Future clinical research that incorporates comprehensive genotyping platforms should greatly advance our knowledge of the pharmacogenetics of drug disposition, improve drug development, and usher in the era of personalized medicine.