A cooperative study between the Department of Otorhinolaryngology and the Highway Safety Research institute of the University of Michigan was designed to study temporal bone fracture produced in cadavers subjected to realistic automotive impact situations. Utilizing sled and piston impact configurations frontal and parietal impacts were noted to produce ipsilateral and contralateral fractures of nine temporal bones in seven cadavers. The impact velocities varied between 18.1 and 25.0 mph. Using standard otologic microsurgical techniques, the temporal bones were dissected and numerous gross and microscopic injuries to middle and inner ear structures were found. The authors conclude that extensive comminuted fracture of the human temporal bone is seen with realistic crash situations of low velocity, and that lateral impact which produces a longitudinal fracture with a posterior fossa comminution is associated with disruption of the cochlea and facial nerve, as well as of middle ear structures. The classical transverse fracture of extensive skull trauma lies medial to these structures and does not involve the otologic contents of the human temporal bone. Associated brain and skull injuries are also described.