Mandatory seat belt legislation has been passed in 15 states. Accompanying this action has been a deluge of information concerning the lives saved and the injuries prevented by the wearing of seat belts by the front seat passengers in automobiles. This study presents data relating to the injuries and deaths attributable to their usage. There is virtually no major area of the adult body that has escaped such involvement. Mechanisms by which seat belt injury is effected are described in relation to the restraint systems currently available in the United States and abroad.