A cooperative study between the Departments of torhinolaryngology and the Highway Safety Research Institute of The University of Michigan was designed to study injuries of the middle and inner ear structures of human temporal bones during realistic automotive impact situations. Seven human cadavers were subjected to either piston side impact or sled impact at velocities ranging between 17 and 25 MPH. Both longitudinal and transverse fractures were seen to occur in the nine temporal bones studied, although significant discrepencies with standard clinical descriptions were apparent. In all cases of lateral piston impact, a longitudinal fracture was present, with a small comminution posteriorly to the region of the posterior cranial fossa. In all of these cadavers, fracture of the cochlea and/or Fallopian canal of the facial nerve was present. Transverse fractures of the petrous apex were present in two cadavers, but in neither was fracture of the cochlea or Fallopian canal present. On the basis of these studies, it would appear that in automotive impact, patients sustaining cochlear or facial nerve injuries are more likely to have a comminuted longitudinal fracture than a classical transverse fracture radiating from the foramen magnum.