Labeling claims for the effectiveness of drugs in the treatment of psychiatric illnesses in children and adolescents must be based on data from adequate and well-controlled investigations. The preferred design for demonstrating the effectiveness of a drug in pediatric psychopharmacology is generally a placebo-controlled trial. Safety information in labeling may be derived from more diverse sources. The Food and Drug Administration (FDA) has taken several steps to encourage more informative labeling of drugs for pediatric use, including a recent labeling initiative that emphasizes the possibility of extrapolating effectiveness data from adult studies to pediatric populations under appropriate circumstances. This recently finalized regulation requires pharmaceutical sponsors to reexamine existing data for their drugs to determine whether there is a sufficient basis for modifying labeling for pediatric use. Included in this new rule is a reminder that in certain situations the FDA may require new pediatric studies, thereby signaling the FDA's determination to improve labeling for the pediatric use of drugs. Improved preclinical models for predicting drug effects on growth and development, as well as improved clinical methods for detecting such changes, need to keep pace with the expansion of research in pediatric psychopharmacology.