Traumatic involvement of the thoracic aorta is of increasing incidence in this highly mechanical age. The early recognition of this condition is important in view of possible surgical intervention. However, considerable diagnostic difficulty may be encountered by the examiner because of the marked degree of variations in the clinical picture. Three cases of involvement of the thoracic aorta following trauma to the thoracic cage are described in detail, and the vagaries of expression of such involvement are enumerated. Report of Cases Case 1. —A 47-year-old white man was admitted to Ancker Hospital on Nov. 30, 1953, with a chief complaint of severe persistent substernal pain which radiated up into the neck. The severe component of the pain began about one week previous to admission. History was elicited to the effect that he had been involved in an argument in the latter part of August of the same year, at which