Seat belt legislation has resulted in increased restraint use by passengers in automobiles in Washington State. At Harborview Medical Center in Seattle, we have observed an increased incidence of seat belt-related injuries. Twenty cases of Chance-type thoracolumbar flexion-distraction fractures were reviewed retrospectively. Thirteen patients (65%) had associated life-threatening intra-abdominal trauma. Twelve of these patients had bowel wall injury. Ninety percent of the children had combined abdominal and spinal injury. Operative treatment of the spinal injury resulted in correction of lumbar kyphosis and lower incidence of back pain than nonoperatively managed cases. We recommend careful physical and radiographic examination of all patients with significant abrasion or bruising about the pelvis or abdomen related to seat belts. Victims of automobile crashes who are treated for bowel injury require thoracolumbar radiographs. Similarly, patients with Chance-type fractures should undergo diagnostic peritoneal lavage or computerized abdominal tomography.