Acute subdural hematoma: morbidity, mortality, and operative timing. Traumatic acute subdural hematoma remains one of the most lethal of all head injuries. Since 1981, it has been strongly held that the critical factor in overall outcome from acute subdural hematoma is timing of operative intervention for clot removal; those operated on within 4 hours of injury may have mortality rates as low as 30% with functional survival rates as high as 65%. Data were reviewed for 1150 severely head-injured patients (Glasgow Coma Scale (GCS) scores 3 to 7) treated at a Level 1 trauma center between 1982 and 1987; 101 of these patients had acute subdural hematoma. Standard treatment protocol included aggressive prehospital resuscitation measures, rapid operative intervention, and aggressive postoperative control of intracranial pressure (ICP). The overall mortality rate was 66%, and 19% had functional recovery. The following variables statistically correlated (p less than 0.05) with outcome; motorcycle accident as a mechanism of injury, age over 65 years, admission GCS score of 3 or 4, and postoperative ICP greater than 45 mm Hg. The time from injury to operative evacuation of the acute subdural hematoma in regard to outcome morbidity and mortality was not statistically significant even when examined at hourly intervals although there were trends indicating that earlier surgery improved outcome. The findings of this study support the pathophysiological evidence that, in acute subdural hematoma, the extent of primary underlying brain injury is more important than the subdural clot itself in dictating outcome; therefore, the ability to control ICP is more critical to outcome than the absolute timing of subdural blood removal. 