In spite of major advances in the management of severe head injury (HI) acute subdural hematoma (ASDH) continues to be one of the most lethal of all intracranial injuries. Of 1,150 consecutive severe HI patients, 137 (12%) had ASDH. The following variables were assessed in regards to outcome morbidity/mortality from ASDH: mechanism of injury, age, sex, neurologic presentation, postoperative intracranial pressure (ICP), and timing from injury to operative evacuation of the ASDH. The only variables found to statistically correlate with outcome were presenting neurologic condition (p = 0.001) and elevated postoperative ICP greater than 45 mm Hg (p = 0.001). The timing from injury to operative evacuation of the ASDH in regards to outcome morbidity/mortality was not statistically significant even when examined at hourly intervals (p = 0.418).