A study was conducted from 1 July 1991 to 30 June 1994 to determine the incidence of blunt traumatic rupture of the thoracic aorta (RTA) in a defined area of inner-metropolitan Sydney. The study group consisted of 30 subjects with RTA following falls, rail or road accidents, who were taken by ambulance to the regional trauma centre or directly to forensic pathology. The incidence of RTA in the resident population of 330,000 was in the range 20-30/10(6)/year. There was one survivor in the series, with 24 scene deaths and five deaths en route to hospital. Road accidents were responsible for 57% of incidents. RTA was found in 36% of the fatalities that occurred as a result of car and motorbike accidents. This was 5 times more common than that observed in pedestrian deaths (P < 0.005). Twenty-seven subjects (90%) had at least one co-existent critical or lethal injury. Outcome may be improved by increasing awareness of the high prevalence of RTA in shocked car- and motor-bike-accident victims and stressing the importance of rapid transport of such cases to an appropriate hospital.