The deaths of two children who were passengers in motor vehicles involved in accidents were directly attributable to vascular injuries derived from seat belts. In the first case, a 10-year-old boy died as a result of abdominal aortic transection by a lap seat belt, and in the second case a 15-year-old boy died as a result of transection of his common carotid artery by a lap-shoulder seat belt. Although these cases demonstrate rare fatalities associated with seat belt use, there is no doubt that seat belts have significantly reduced mortality and morbidity from traffic accidents. Although it is possible that a fatal outcome might have occurred in each of these cases from other injuries that might have been sustained had seat belts not been worn, appropriate positioning and size of seat belt harnesses might have avoided the lethal injuries.