Older views of the functional developmental plasticity of the developing central nervous system (CNS) focused on the protective effect of a young age at the time of insult. In these views, a younger rather than an older age at onset was thought to produce fewer and/or less severe symptoms and a more rapid recovery. More recently, neurobehavioral outcome has been studied in a variety of medical conditions that affect the developing CNS; at the same time, new investigative techniques, such as brain imaging, have elucidated the biological basis of structural and functional brain plasticity. In consequence of a better understanding of the structural and functional consequences of developmental CNS insults, a body of research has emerged that is shaping a new view of functional developmental plasticity, in which neurobehavioral outcome is set by the biological risk associated with a medical condition and moderated by age and development, the time since onset of the condition, and the reserve available within the child, family, school, and community. (C) 2000 by Elsevier Science Inc.