Background: Screening for abdominal aortic aneurysm (AAA) has been carried out in Gloucestershire since 1990. All men in the county are offered aortic ultrasonography in their 65th year. Men with an aortic diameter of less than 26 mm are considered 'normal' and no follow-up is arranged. The aim of this study was to ascertain if men with 'normal' aortic diameters at age 65 years ever develop a clinically significant aneurysm. Methods: A cohort study was performed on 223 65-year-old men who had an aorta of less than 26 mm in diameter in 1988. These men had repeat ultrasonography in 1993 and 2000. The causes of death in men who died during this interval were investigated. Results: Eight men were lost to follow-up. As far as it was possible to ascertain, none of the 86 men who died over the 12-year interval did so from ruptured AAA. There was no clinically significant increase in mean aortic diameter in the remaining 129 men who had three serial ultrasonographic scans over the 12-year interval. Conclusion: A single, 'normal' ultrasound scan at age 65 years effectively rules out the risk of clinically significant aneurysm disease for life in men.