In order to analyze the possible benefits on the mortality of abdominal aortic aneurysms (AAA) in Viborg county from the establishment of a specialized vascular unit in the county, the periods just before (1986-1988) and just after (1989-1991) the start of the unit were reviewed. Three times as many operations for AAA (104/mill/yr) were carried out after the unit opened. Acute operations increased sevenfold. In 1986-1988 42 persons experienced rupture of AAA. Twenty-six (63%) died outside hospital. Thirteen (32%) died at primary receiving hospitals. Only three patients (7%) were operated. One survived, making the overall mortality 97.5%. The mortality in this period was 187/million persons over 50 years. In 1989-1991 39 persons experienced rupture. Eleven (28%) died outside hospital. Eight (20.5%) died at primary receiving hospitals. One died preoperatively on the vascular unit. Nineteen (49%) reached operation, 13 survived (33%) and six (15.4%) died postoperatively. The overall mortality was 67%, the mortality of AAA was 127/million persons over 50 years. Comparing the two periods, deaths, mortality and overall mortality due to ruptured AAA decreased by 32% after the introduction of the vascular unit.