Although individual reports have indicated that a fracture of the first or second rib is predictive of injury to the thoracic aorta and its major branches, the results of a careful review of the literature do not support this contention. In patients suffering blunt trauma, the risk of disruption of the aorta is not greater in patients with fracture of the upper two ribs, compared with victims of trauma with fracture of other ribs or those without fracture of ribs. Clinical manifestations are often absent in patients with disruption of the aorta or the innominate artery, but evidence of mediastinal hemorrhage is almost always present on roentgenograms of the chest. Widening of the mediastinum may not be apparent, but obliteration of the normal aortic contour is a sensitive finding in aortic transection. Injury to the subclavian or carotid artery nearly always produces clinical or roentgenographic signs, or both. After blunt trauma to the chest, patients with fracture of the first or second rib without clinical signs of vascular injury and evidence of mediastinal hemorrhage on thoracic roentgenograms (with the patient in an upright position when possible) do not need aortography to exclude occult vascular injury. A few patients with injury to the great vessels may have a normal thoracic roentgenogram on initial presentation to the hospital. After the correction of hypovolemia and stabilization of hemodynamic status, evidence of mediastinal bleeding should become apparent on subsequent thoracic roentgenograms. Repeat examinations must be performed and serial roentgenograms of the chest must be obtained for several days after injury to assess the possibility of unrecognized vascular trauma. If clinical or roentgenographic evidence of vascular injury is revealed, arteriography is mandatory. Thoracic CT scanning in patients with evidence of mediastinal hemorrhage on plain film may be of value in selecting patients for angiography, but additional experience must be obtained before such a protocol becomes an established policy.