Employment of seat belts reduces the number of fatal accidents and alters the pattern of lesions. However, seat belts themselves can produce serious lesions, particularly if incorrectly placed. Three cases of traumatic intestinal perforation are mentioned. Intestinal perforation often produces few initial symptoms. The diagnosis is difficult and is frequently established late. If marks are present on the abdomen from the seat belt, the patient should be admitted for observation. The possible pathogenesis of the intestinal lesions are mentioned. The seat belt should be correctly placed in order to obtain optimal effect. Reasons for incorrect placing are mentioned. It is important that the seat belt is adjusted to the passenger employing it.