Child and adolescent psychologic development is a complex process that is governed by the interactions of multiple biologic, genetic, sociocultural, and environmental variables. Viewed from an ecological context, the individual influences, and is influenced by, a multilayered set of systems, including the family, school, neighborhood, and peer group, as well as the more indirect effects of the workplace, health care and social services systems, and the larger cultural belief and value systems of the society in which the individual lives. This article reviews the major developmental themes and transitions through which children and adolescents must move on the path to adulthood. Primary developmental tasks are reviewed within each age period from birth to adulthood, along with a discussion of several risk factors that present challenges to normal development at the individual, family, community, and societal levels. The important roles of pediatricians and other health care professionals in helping children and families negotiate these developmental challenges is also reviewed.