We studied 26 cases of abdominal aortic aneurysm with magnetic resonance imaging (MRI), computed tomography (CT), ultrasonography (US), and angiography. Data acquired were compared to those obtained at surgery. Diameter of the aneurysm was correctly defined in all cases by CT and MRI, while angiography underestimated the diameter of lesions without peripheral calcifications. Involvement of renal arteries was present in four cases and correctly diagnosed with MRI and angiography in all of them. CT did provide this information in three cases and US were not useful. Also, iliac arteries involvement was depicted by CT, MRI, and angiography in 10 out of 10 patients. Coronal sections of MRI provided comparable images to those of angiography. By comparing these different techniques we verified the good reliability of MRI as investigation tool for an accurate evaluation of aneurysms; its only limit lying in the poor capability of detecting calcifications.