Sporadic cases of vertebral artery occlusion following neck manipulation have been reported since 1947. The pathogenesis of occlusion, however, has remained largely speculative. Autopsy examination of the intracranial and extracranial portions of the vertebral arteries in the case presented here clearly demonstrates that intramural hematoma arising within granulation tissue in the tunica media was the acute, occlusive event. Furthermore, prior neck manipulation may have caused asymptomatic development of granulation tissue within the tunica media, thereby predisposing the patient to acute intramural hematoma during subsequent neck manipulation.