Compared with adults, children and adolescents respond to psychotropic medications in some distinctive ways that have implications for both efficacy and safety. Age-related differences in pharmacokinetics and pharmacodynamics account for some of these differences. But while the disposition of several psychotropics in children has been studied, the pharmacodynamic effects of the interaction between the drug and the developing brain are still largely unknown. There is now evidence that the major neurotransmitter systems undergo developmental changes that can extend into the second decade of life. Data from various animal models also show that the administration of psychotropics in the pre-and perinatal period can interfere with the development and produce permanent changes in the neurotransmitter system in question. The extrapolation of these data to humans is difficult. Given the increase use of psychotropics in the pediatric age, the need emerges for systematic investigation on long-term effects of these drugs on the developing brain.