On the basis of 72 radio-surgical cases of abdominal aortic aneurism, the authors stress the value of atypical angiographic findings, which are ten in number. The presence of clot within the aneurism itself may explain a disparity between radiological and surgical findings. Failure to recognize these atypical signs is very serious, when the diagnosis of aneurism is not suspected clinically. Antero-posterior and, above all, lateral abdominal aortography is essential in the angiographic study of aneurisms of the abdominal aorta. Careful search for these 10 atypical signs should make it possible to avoid missing latent aneurisms. Lateral abdominal aortography is essential in order to determine the state of the abdominal collaterals of the aorta and, in particular, the superior mesenteric artery.