The lethality of ruptured abdominal aortic aneurysm (AAA) is 80-95% compared to 5-6% after elective surgery. However, AAA seldom causes symptoms before rupture. From 1994 to 1998, 12,639 men aged 64-73, from Viborg County, were randomised 1:1 for an invitation to an ultrasonographic scan or for controls. There were 75% fewer emergency operations (P < 0.001), and 67% lower AAA-specific mortality in the screening group (P = 0.002). The costs were 6,221 pounds sterling (4,034-13,782) per saved living year, expected to decrease to about 1,860 pounds sterling after 10 years. Screening of Danish men, aged 65-73, is recommended.