Pharmacogenomics and pharmacogenetics provide methodologies that can lead to DNA-based tests to improve drug selection, identify optimal dosing, maximize drug efficacy or minimize the risk of toxicity. Rapid advances in basic research have identified many opportunities for the development of 'personalized' treatments for individuals and/or subsets of patients defined by genetic and/or genomic tests. However, the integration of these tests into routine clinical practice remains a major multidisciplinary challenge, and even for well-established biomarkers there has been little progress. Here, we consider this challenge from a regulatory perspective, highlighting recent initiatives from the FDA that aim to facilitate the integration of pharmacogenetics and pharmacogenomics into drug development and clinical practice.