A 35-year-old man was witnessed to be held by two other men and struck in the face with an object by a third man. The impact caused his head to abruptly extend backward and rotate to his left. An autopsy was conducted revealing subarachnoid hemorrhage (SAH). SAH is the most common intracranial lesion seen in cases of blunt force head injuries. SAH was the sole traumatic intracranial finding in less than 1 percent of fatal head trauma cases. Identifying SAH as a traumatic cause of death can be difficult, particularly in those instances in which the SAH is the sole intracranial finding, because the degree of external injury is sometimes so slight that the visible signs of trauma are frequently judged to be of insufficient magnitude to account for the development of the hematoma. In this case, the man had a SAH arising from a clearly demonstrable tear in the intracranial portion of the right internal carotid artery, with an atheromatous plaque near the disrupted area of the vessel. It was postulated that the forces acting on the head during abrupt hyperextension and rotation, in combination with the alteration and possible compromise of the vessel wall by atherosclerosis, were responsible for this unusual and fatal injury. Plaques in the carotid arteries of middle-aged Americans may contribute to alteration or focal destruction of arterial wall structural elements. This disruption of structural integrity of vessels at the site of atherosclerotic plaques, coupled with decreased elasticity and impaired ability to compensate for rapid increases in intraluminal pressure, may act to focally predispose vessels to laceration secondary to trauma. 4 figures, 11 references