The strange and harrowing sight of a person being awake but unaware with no evidence of a working mind - the characteristics of the vegetative state - provokes intense debate and raises profound questions for health professionals, ethicists, philosophers and lawyers. This unique account by an unrivalled expert in the field, who himself collaborated in coining the term 'persistent vegetative state', surveys the medical, ethical and legal issues that surround this controversial topic. The medical definition and criteria for diagnosis are discussed, as are its frequency and causes, and possible outcomes. Ethical arguments discussed include the conflict between sanctity of life and respect for the autonomy and best interests of the victim, and between killing and letting die. Legal issues are explored with details of landmark court cases from the USA, Britain and elsewhere. This well-informed and carefully constructed account will be a benchmark for medical specialists, ethicists, lawyers and philosophers.