The city of Malmö (population approximately 230,000) has a fairly stable urban population and a high autopsy rate (83 per cent of all deaths). Autopsy records for the period from 1958 to 1985 were scrutinized and three groups of patients were defined: those with asymptomatic thoracic aortic aneurysm (TAA), those with rupture of the thoracic aorta, and those with dissection. The findings were used to calculate prevalence and incidence according to age and sex. Asymptomatic TAA was found in 205 patients (109 men). There was a predominance of men in higher age groups and about 5 per cent of the lesions were thoracoabdominal. Rupture of the thoracic aorta was the cause of death in 63 patients; no age difference between the sexes was observed. Death as a result of dissection occurred in 216 patients, women dying on average 7 years later than men. The incidence of rupture was 0.9 per 100,000 for men and 1.0 per 100,000 for women; the incidence of dissection was 3.2 per 100,000 for both sexes. Prevalence and incidence of fatal complications of TAA are low; this may influence decisions about where these patients should be treated.