Among the five major decelerational thoracic injuries [myocardial contusion (MC), traumatic aortic disruption (TAD), sternal fracture (SF), flail chest (FC), and tracheobronchial disruption (TBD)], coexisting injuries are seemingly rare.To test this hypothesis, we reviewed the records of all patients, with final diagnosis (FDX) codes of these injuries, treated at our Level I trauma center for the 10 years preceding 1997.Among 142 patients, all victims of motor vehicle crashes, there were 38 MC, 36 TAD, 33 FC, 28 SF, and 7 TBD. There were six coexisting injuries (3.5%). Three patients with coexisting injury died in the operating room. All three had TAD; one of these three had TBD plus MC; one had additionally FC and MC and the third had FC in addition to the TAD. One patient with SF and probable MC died in the emergency room. Two patients with FC and a coexisting injury survived. One had MC, the other SF.We conclude that these decelerational thoracic injuries, with the exception of sternal fracture, are sufficiently life threatening by themselves to cause fatality. When combined, the threat to life is potentiated. Death occurs at the scene or shortly after arrival in the ER. The diagnosis of one may help exclude the diagnosis of each of the other four. The role of sternal fracture in this paradigm remains an enigma.