Traumatic brain injury (TBI) is a major cause of death and disability in developed societies. Every year, approximately 3.5 million Americans sustain a TBI, of which 50,000 die, and another 300,000 are hospitalized and survive the injury. This proposed study focuses on the most severely injured of this group, approximately 27,000 Americans each year who experience prolonged coma from a TBI, and require sophisticated care in neurological Intensive Care Units. This group experiences high rates of mortality and morbidity, and only 20% make a good recovery resulting in an enormous psychosocial burden on patients, their families, and society. This study proposes to determine whether a treatment protocol based on brain tissue oxygen monitoring, using technology that has been available for over 10 years, improves neurologic outcome in this most severely injured group of patients.