The types and severity of injuries of 49,143 patients from 95 trauma centers were coded according to the 1985 version of the Abbreviated Injury Scale (AIS). This paper analyzes the causes, incidence, and mortality in 16,524 patients (33.6% of the trauma center patients) with injury to the brain or skull and compares them to patients without head injury. Relative to its incidence, patients with head injury composed a disproportionately high percentage (60%) of all the deaths. This was due to the high mortality rate for head-injured patients. Overall mortality of patients with head injury (18.2%) was three times higher than if no head injury occurred (6.1%). This mortality was little influenced by extracranial injuries except when minor and moderate head injuries were accompanied by very severe (AIS levels 4 to 6) injuries elsewhere. The cause of death in head-injured patients was approximated and it was found that 67.8% were due to head injury, 6.6% to extracranial injury, and 25.6% to both. Head injury is thus associated with more deaths (3,010 vs. 1,972) than all other injuries and causes almost as many deaths (2,040 vs. 2,170) as extracranial injuries. Because of its high mortality, head injury is the single largest contributor to trauma center deaths.