The availability of the human genome sequence and the increasing knowledge of functional polymorphisms will highlight new therapeutic approaches to treat diseases with unmet medical need and will allow the targeting of new and existing therapies to those patients who will derive the most benefit without the risk of serious side effects. This review describes how genetic information can be used to improve the drug discovery and development process. It should be emphasized, however, that although it is anticipated that high-throughput genetic studies will provide novel biological insights into disease, it is not a replacement for careful hypothesis-driven experiments. Rather, it is essential to combine genetic studies with carefully conducted preclinical and clinical experiments to extract the true value of high-throughput genetics-based research.