Over the 19-month period November 7th, 1984 to June 11th, 1986, 200 consecutive autopsies were conducted on victims of motor vehicle accidents. In each case, both common carotid arteries and their respective internal and external branches up to 2 cm beyond the bifurcation were examined for evidence of contusion, partial tearing or rupture. All lacerations or disruptions were excised together with a segment of surrounding arterial tissue, and processed, sectioned and examined by conventional light microscopy for the presence and extent of arterial tears. Several findings emerged: (i) in nearly one-third of subjects there was some degree of arterial disruption; (ii) dual or even triple vessel involvement in both an ipsilateral and contralateral distribution occurred in 38.6% of the 57 subjects in whom traumatic arterial lesions were found; (iii) the large number of intimal disruptions encountered, 44.7% of which showed extension of the tear to the internal elastic lamina with further longitudinal continuation of the tear along the lamina without breaching it; (iv) tears along the laminar planes of the media occurred in 52.6% of the 57 subjects and was particularly apparent at sites of subsidiary vessel bifurcation; (v) compound intimo-medial tears occurred in almost two-thirds (63.2%) of the 57 subjects, highlighting the dual involvement of these layers of the arterial wall in traumatic lesions; (vi) the occurrence of adventitial contusions in 70.2% of the 57 subjects; (vii) the occurrence of complete vessel wall transection in more than one-quarter (26.3%) of the vessels with positive findings and involving nearly one-third (31.6%) of subjects, indicating perhaps the severity of the trauma to which the victims were exposed.