This book integrates clinical and research findings on catastrophic brain injury. The clinical chapters address the definition, epidemiology, pathophysiology, and outcomes of the most severe closed head injuries that typically result in death or neurobehavioural sequelae. The chapters on experimental research include reviews of recent advances in characterizing neurochemical interactions contributing to secondary brain injury.A summary chapter synthesizes the clinical and experimental material, provides an update concerning ongoing clinical trials, and offers a perspective on future directions of research to mitigate the consequences of severe head injury.