Great strides have been made in the past several decades in clarifying brain behavior relationships. Most of the research has focused on the direct effects of a brain injury on behavioral functioning. Only recently has attention been given to documenting the mechanisms by which the disruption of various organs and systems compromise cerebral integrity and ultimately how such disruption affects cognition and behavior. It is this relatively new topic of inquiry, medical neuropsychology, that comprises the subject of this book. As will be noted, the chapters are organized on a system-by-system basis. Each of the organ systems contributes in a unique and specialized fashion to maintaining the integrity of brain functioning. Thus, the chapters by Prigatano and Levin, Stanton, and Ryan address the consequences of disturbed energy regulation and oxygen supply. Other chapters, specifically those by Tarter, Edwards, and Van Thiel and by Hart and Kreutzer examine the effects on the brain when the liver and kidney cannot efficiently cata bolize or eliminate cerebrotoxic substances. The effects of metabolic disrup tion mediated through pituitary and thyroid gland mechanisms illustrate the complex and synergistic relationship among the various organs and systems and the brain. As discussed by Gordon, Lee, and Tamres, diverse intercorre lated processes regulate physical growth, cerebral specialization of function, and complex cognitive capacities. Beckwith and Tucker underscore the in terrelationships among cognitive, affective, behavioral, and neurophysio logical processes pertinent to thyroid functioning. The book concludes with discussions of three rather specialized topics of current interest.