To determine which clinical and radiographic findings are valuable in selecting patients with blunt chest trauma for aortography, we analyzed the medical records and admission chest radiographs of 76 consecutive victims of blunt chest trauma with suspected thoracic aortic rupture during the past 7 years. All patients were evaluated by history, physical examination, chest radiography, and aortography; a total of 70 clinical and radiographic findings were independently assessed in each patient. The following occurred with significantly greater frequency in patients with thoracic aortic rupture than in those without: history of significant hypotension (mean arterial pressure less than 80 mm Hg) (p less than 0.04); the presence of upper extremity hypertension, bilateral lower extremity pulse pulse deficits, or an initial chest tube output greater than 750 ml of blood (p less than 0.05); and greater incidence of myocardial contusions, intra-abdominal injuries, and pelvic fractures compared with patients without thoracic aortic rupture (p less than 0.05). Mediastinal widening (equal to or greater than 8 cm) shown on anteroposterior chest radiography occurred in all patients with thoracic aortic rupture; however, its specificity was only 10.6%. Radiographic signs that were helpful in indicating the presence of thoracic aortic rupture included paratracheal stripe greater than 5 mm, rightward deviation of the nasogastric tube or central venous pressure line, blurring of the aortic knob, and an abnormal or absent paraspinous stripe. Upper rib fractures and mediastinal to thoracic cage width ratios at any level did not increase diagnostic accuracy for thoracic aortic rupture in the present series. Six patients in the series died, two of whom had thoracic aortic rupture.(ABSTRACT TRUNCATED AT 250 WORDS)