Twenty-four cases of abdominal aortic aneurysm were studied by means of MR Imaging, Computed Tomography (CT), Ultrasound (US) and Angiography. MR Imaging gave detailed information on the site and extension of the aneurysm. The extent of branches involvement, the presence of thrombosis, and the adjacent structures were also demonstrated. Major limitations of angiography were its morbility, and the difficult/impossible demonstration of eventual thrombi, and of the adjacent structures. CT, although extremely valuable in emergency cases and in the detection of calcifications, provided insufficient information on the involvement of the vessels originating from the aorta. US proved useful in the screening of abdominal aortic aneurysms, but lacked both the accuracy and the reliability necessary to a complete preoperative evaluation. MR Imaging proves thus to be a good investigation technique for a complete assessment of aneurysmatic lesions. Its major limitation is its inability to detect calcifications, while its major advantages are the accurate demonstration of both blood flow and eventual thrombi, and the multiplanarity and non-invasiveness of the methodology.