An Abdominal Aortic Aneurysm (AAA) is a weakening in the wall of the abdominal section of the aorta, which is the largest artery in the body. Once a section of the aortic wall is weakened, the pressure from the blood flowing through causes the aorta to bulge or balloon, resulting in the formation of an aneurysm. A large proportion of AAAs are asymptomatic until the development of rupture. AAA rupture can be acute and is life-threatening. The most accepted definition of an AAA is based on the diameter of the artery, with a diameter of 3.0 cm or larger considered to be an aneurysm. This is more than two standard deviations (SDs) above the average diameter of the abdominal aorta (2.0 cm) in both men and women. The abdominal aorta diameter varies somewhat by age, sex, and body size, which may influence the accuracy of this definition in some subgroups. An AAA is also defined as a maximum infrarenal aortic diameter of at least 1.5 times larger than the expected infrarenal aortic diameter. This definition, however, is less frequently used. The U.S. Preventive Services Task Force (USPSTF) commissioned this report to update the previous recommendation on abdominal aortic aneurysm (AAA) screening. In 2005, the USPSTF found good-quality evidence to recommend one-time screening for AAA by ultrasonography in men ages 65 to 75 years who have ever smoked (B recommendation). The USPSTF concluded that the benefits of screening do not clearly outweigh the possible harms in men ages 65 to 75 years who have never smoked, and thus made no recommendation for or against screening for AAA in this population (C recommendation). Also, based on the low prevalence of the condition and its sequealae and the presence of competing risks, the USPSTF recommended against routine screening for AAA in women age 65 years and older (D recommendation). This study applied systematic review methods to systematically assess the evidence regarding the benefits and harms of AAA screening and alternative strategies for managing screen-detected small AAA.