The Department of Veterans Affairs Cooperative Studies Program has completed two studies on abdominal aortic aneurysm (AAA) and is currently conducting a third. The first, the Aneurysm Detection and Management (ADAM) Study, consisted of both a screening program, which provided information on the prevalence and associations of AAA, and a randomized trial, which found that survival is not improved by repair of small AAA. The second was a prospective observational study to determine the incidence of rupture in patients with large AAA for whom elective repair was not planned due to medical contraindications or patient refusal. AAA in this population had a high risk of rupture, about 10% per year for AAA > 5.5 cm, and 25% within 6 months for AAA larger than 8.0 cm. The third, the Open Versus Endovascular Repair (OVER) Trial, is a multicenter randomized trial comparing long-term survival following two methods of elective AAA repair.