The cause of death was determined in the autopsy when microscopic examination of serial sections of the entire left internal carotid artery revealed a partial dissection in the subadventitial layer at the proximal level. This subadventitial dissection progressively extended around the entire circumference so that the media with intima (inner wall) was prominently displaced. As the artery was completely dissected through the subadventitial layer, a false lumen was created, containing the inner wall originating from the lower portion of the vessel. The inner wall was pushed upward into the false lumen which was completely occluded by a recent thrombus. The frequency of blunt trauma to the neck is relatively high in traffic accidents; however, injury to the internal carotid artery as a result of blunt trauma is uncommon. Dissection of the internal carotid artery may be caused by various types of injuries, but many patients with dissection of the internal carotid artery are involved in motor vehicle accidents. The cerebral manifestations of traumatic internal carotid artery dissections are usually focal neurologic deficits due to carotid artery insufficiency including hemiparesis, monoparesis, aphasia, hemianopsia, convulsions, and alteration in the level of consciousness. The onset of neurological symptoms due to traumatic dissection of the internal carotid artery is most often delayed following traumatic events. Attention should be paid to those patients who do not show any evidence of neck injury, but develop delayed symptoms and rapid fatal course. 5 figures and 6 references