Axial loading injuries to the middle cervical spine segment. An analysis and classification of twenty-five cases. Injuries to the cervical spine at the C3-C4 level involving the bony elements, intervertebral disks, and ligamentous structures are rare. We present 25 cases of traumatic C3-C4 injuries sustained by young athletes and documented by the National Football Head and Neck Injury Registry. Review of the cases reveals that the response of energy inputs at the C3-C4 level differ from those involving the upper (C1-C2) and lower (C4-C5-C6-C7) cervical segments. Specifically, the C3-C4 lesions appear to be unique with regard to the infrequency of bony fracture, difficulty in effecting and maintaining reduction, and a more favorable recovery following early, aggressive treatment. In the majority of instances, injury at this level results from axial loading of the cervical spine. Lesions were distributed into specific categories: 1) acute intervertebral disc herniation (N = 4), 2) anterior subluxation of C3 on C4 (N = 4), 3) unilateral facet dislocation (N = 6), 4) bilateral facet dislocation (N = 7), and 5) fracture of vertebral body C4 (N = 4). Analysis of these 25 cases suggests that traumatic lesions of the cervical spine in general can be classified as involving the upper (C1-C2), middle (C3-C4), or lower (C4-C7) segments. This is based on our observations from this series that C3-C4 lesions 1) generally do not involve fracture of the bony elements; 2) acute intervertebral disc herniations are frequently associated with transient quadriplegia; 3) reduction of anterior subluxation of C3 on C4 is difficult to maintain; 4) reduction of unilateral facet dislocation is difficult to obtain by skeletal traction and is best managed by closed manipulation and reduction under general anesthesia; and 5) reduction of bilateral facet dislocation is difficult to obtain by skeletal traction and is best managed by open methods. The more favorable results observed in this series of immediate reduction of both unilateral and bilateral facet dislocations deserves emphasis. In two cases of unilateral facet dislocation reduced within 3 hours of injury and subsequently fused anteriorly, significant neurologic recovery occurred. The other four patients, two who underwent an open reduction and laminectomy and two treated closed with skeletal traction, remained quadriplegic. In the four instances of bilateral facet dislocation where reduction was achieved by either closed or open methods, although there was no neurologic recovery, all four patients survived their injuries. However, the three patients who were not successfully reduced died. 