A case of nonketotic hyperglycemic hyperosmolar coma occurring in a patient with closed head injury and basilar skull fracture is reported. The metabolic abnormality masqueraded as a progression of central transtentorial herniation due to cerebral edema. It is suggested that the development of this complication is related to various predisposing factors normally employed in cases of critically ill, neurologically compromised patients. The anatomic lesions found at autopsy were considered inappropriate as a cause of death; the occurrence of central transtentorial herniation three days before death had been reversed. An awareness of this syndrome is emphasized in considering patients receiving steroids, mannitol, tube feedings, Dilantin, and dehydrative measures as part of their care.