The study of individual genes involved in drug metabolism goes back to the 1960s. The conceptual hope in a move from genetics to genomics is that with modern automated technology, it will be possible to examine the impact of an individual’s genomic composition as a whole on that individual’s response to therapy. These technologies include the use of DNA microarrays to screen up to 100,000 single-nucleotide polymorphisms (SNPs) found in a patient’s genome in a matter of hours. SNP, pronounced “snip,” refers to the variation within an individual’s DNA. Proteomics, the study of protein products of these gene variations, likewise has been automated, allowing for broad screening. Transplant clinicians have long known that patients respond differently to organ transplantation and the therapies used to prevent rejection. It is hoped that by using differential gene expression, genetic profiles of these responses will be determined and therapy will be tailored appropriately.