The pathogenesis of cord damage in hyperextension injuries of the cervical spine was studied by the clinical and roentgenographic features in forty-five patients with such an injury, by autopsy in four patients who died with this injury, and in seven cadavera in which the injury was induced. The results of the study showed that the cord is damaged in an anteroposterior direction by the squeezing effect produced between a backward subluxating vertebral body at the disc-space level, or through a complete fracture of the vertebral body just below the pedicle anteriorly and an infolded ligamentum fiavum posteriorly. The mechanism of injury is a combination of hyperextension and backward shearing forces.