Patients at ages of neonate and infant are at developmental ages facing special challenges on drug therapy and toxicity. Most prescription drugs are used as off label for neonates and infants. They have the highest medical errors and adverse drug action rates. There is a specific requirement for inclusion of neonates and infants as a study population for therapeutic efficacy, toxicity, and development of new drugs. Several knowledge gaps exist, making too difficult to study neonates and infants. The aim of the symposium is to bring several experts in the field to discuss studies of ADME at these specific ages.