The aorta, a large blood vessel that passes through the chest and abdomen, carries blood from the heart to the body. Abdominal aortic aneurysms (AAAs) are bulges in weakened sections of the aorta. They are most common in men older than age 65 years, people with high blood pressure, and smokers. Large aneurysms can burst or rupture, which often causes death. Thus, the general recommendation is for patients with AAAs larger than 5.5 centimeters to have surgery to fix the aorta. Most patients experience no symptoms from AAAs until rupture nears. Ultrasonography is the best test to look for AAA. Screening for AAA involves performing ultrasonography in people who have normal findings on physical examination and no symptoms. The goal of screening is to find AAAs and, if they are large enough, fix them before rupture. Surgery to fix AAAs is a major procedure and can have serious complications, including death. Screening for AAAs has not become regular practice because the benefits compared with the risks have been unclear.