Pharmacogenetic and pharmacogenomic investigations conducted in children must consider that human development from conception through to adolescence is a rapidly changing, dynamic process. An improved understanding of the gene networks that are involved in growth and development and of the unintended consequences of modulating those systems could provide insights into the susceptibility of an individual to drug-induced birth defects and to pediatric adverse drug reactions. Furthermore, these technologies potentially present the opportunity to develop novel, effective treatments for childhood diseases and for adult diseases that manifest primarily during childhood. The lack of pharmacogenetic and pharmacogenomic investigations in children and the potential to impact on all age groups provides a considerable incentive to invest in this area of research.