Rett disorder, first described by Andreas Rett in 1966, is a condition which involves the functions on which intelligence and expression depend. It is probably the most common genetic disorder encountered in profoundly intellectually disabled females. Its many manifestations include epilepsy, scoliosis, nutritional difficulties, and disorders of mood and movement. This book provides an up-to-date account of current research into the disorder at a time when the causative mutations have just been discovered on the MeCP2 gene. The first section of the book presents the clinical signs and the latest research into the genetic, neuro- anatomical and neuro-chemical aspects of Rett disorder. The second section moves on to deal with the neuro-physiological research, concentrating on the autonomic system, which is deeply implicated in the disease mechanisms. The final section of the book examines the behavioural and psychological features of Rett disorder and discusses issues relating to communication. The chapters are written by a distinguished, international team of experts, all currently active in research. The contributions bring our understanding of the Rett disorder right up-to-date, as the study of the condition moves from an era of description into a time when there are real possibilities for beneficial interventions.