Increased use of thoracic CT (TCT) in diagnosis of blunt traumatic injury has identified many injuries previously undetected on screening chest x-ray (CXR), termed "occult injury". The optimal management of occult rib fractures, pneumothoraces (PTX), hemothoraces (HTX), and pulmonary contusions is uncertain. Our objective was to determine the current management and clinical outcome of these occult blunt thoracic injuries. A retrospective review identified patients with blunt thoracic trauma who underwent both CXR and TCT over a 2-year period at a Level I urban trauma center. Patients with acute rib fractures, PTX, HTX, or pulmonary contusion on TCT were included. Patient groups analyzed included: (1) no injury (normal CXR, normal TCT, n=1337); (2) occult injury (normal CXR, abnormal TCT, n=205); and (3) overt injury (abnormal CXR, abnormal TCT, n=227). Patients with overt injury required significantly more mechanical ventilation and had greater mortality than either occult or no injury patients. Occult and no injury patients had similar ventilator needs and mortality, but occult injury patients remained hospitalized longer. No patient with isolated occult thoracic injury required intubation or tube thoracostomy. Occult injuries, diagnosed by TCT only, have minimal clinical consequences but attract increased hospital resources.