Safe and effective drug therapy in neonates, infants and children require detailed knowledge about the ontogeny of drug disposition and action as well how these interact with genetics and co-morbidity in children. Recent advances in developmental pharmacology in children follow the increased understanding of the impact of growth and development on drug disposition (absorption, distribution, metabolism and excretion–ADME). Numerous approaches have been used to determine optimal dosing of drugs in children, none of which are perfect. Human growth is a non-linear process and age-related changes in body composition and organ function are dynamic and often discordant during infancy. Major gaps of knowledge remain regarding the ontogeny of drug metabolizing enzymes and transporting proteins, and the paucity of pharmacodynamic and pharmacogenetic data in the paediatric population remains overwhelming.