To assess the age- and sex-specific prevalence and risk factors for aneurysms of the abdominal aorta, the authors performed a population-based study in 5,419 subjects (42% men, 58% women) aged 55 years and over. The proximal and distal diameter of the abdominal aorta were measured by ultrasound. An aneurysm was defined as a distal aortic diameter of 35 mm or more or a dilatation of the distal part of the abdominal aorta of 50% or more. The mean distal and proximal aortic diameter increased 0.7 mm and 0.3 mm, respectively, with every 10 years of age. In 2.1% (95% confidence interval (Cl) 1.7–2.5) of the study population, an aneurysm was present, or in 4.1% (95% Cl 3.2–4.9) of the men and 0.7% (95% Cl 0.4–1.0) of the women. Subjects with an abdominal aneurysm were more likely to besmokers and they had higher serum cholesterol levels and higher prevalence of cardiovascular disease compared with subjects without an aneurysm. The authors conclude that the ultrasound diameter of the abdominal aorta clearly increases with age in both men and women and that the prevalence of aneurysms of the abdominal aorta in older adults isrelatively high, especially in men.