Fewer than 140 cases of aortic sarcoma have been reported with only 34 classified as angiosarcoma. These rare malignancies most often mimic aortoiliac occlusive or aneurysmal arteriosclerotic disease both clinically and on imaging studies, and the large majority are unexpected and diagnosed pathologically on a surgical specimen or at autopsy. A 42-year-old woman who presented with low back pain and claudication was shown by CT and angiography to have infrarenal aortic occlusion. Angiosarcoma was an unexpected pathologic diagnosis based on tissue removed during aortobifemoral bypass surgery. Pre and postoperative CT and angiography are presented along with a review of the literature.