In the first case, the driver of the case vehicle hit another car in such a way that the driver's door was forced open and the driver propelled toward the resulting opening. Because the driver was wearing only the two-point shoulder harness, his neck and upper torso were anchored by the restraint as his unrestrained hips and lower extremities continued to move. The momentum of his lower body against his restrained neck led to decapitation. In the second case, the crash involved a frontal crash in which the occupant's lower body, unanchored without a manual lap belt, moved forward with terrific force while the automatic two-point shoulder harness restrained her at the neck and chin, causing a near complete decapitation. The third case involved a similar front end crash in which the vehicle's occupant was unrestrained by a lap belt but restrained by an automatic two-point shoulder harness, causing her trachea to be transected through the cricoid cartilage, along with injury to the second cervical vertebra. In the fourth case, the right front occupant was ejected from the vehicle in the course of the vehicle's roll-over. As she was being ejected, the shoulder restraint pressed against her neck with sufficient force to cause fatal injuries. Based on these and other case studies, the authors advise that the use of an automatic two-point shoulder harness without concurrent use of a lap belt may be associated with severe neck trauma that can involve cervical spine fractures and rarely decapitation. 4 figures and 26 references