Abdominal computed tomography was performed in six patients with suspected ruptured abdominal aortic aneurysm but in whom an alternate clinical diagnosis was seriously considered. In each patient, a large aortic aneurysm was demonstrated in association with a retroperitoneal accumulation of high-density blood. The retroperitoneal blood was primarily confined to the extracapsular perinephric space. In four of the six patients, a focal area of the aortic wall was indistinct on the side of the retroperitoneal hemorrhage at the presumed site of rupture. Five of the six patients underwent emergency surgery, which confirmed the site of aneurysm, presence of rupture, and the location of fresh retroperitoneal blood.