Magnetic resonance (MR) imaging provides detailed evaluation of cardiovascular structures, due to high intrinsic contrast between flowing blood and vessel's lumen. Early application have shown the clinical validity of the technique, with non-invasive, multiplanar imaging of large and medium sized vessels. In this study we evaluate the capabilities of MR in screening out patients with thoracic aorta enlargement. Examination has been performed in 16 patients, employing a 0.5 T superconductive unit, and acquiring images on axial, sagittal and coronal planes with 7 mm slice thickness. In 15 cases it was possible to detect the pathology and to characterize it according to type, location and extension. In 1 case it was no possible to make an accurate diagnosis for the presence of movement artefacts, due to poor patient's cooperation. In dissecting aneurysms the true and false lumen may be differentiated, with a good visualization of the intimal flap. The relation between the origin of the aortic branches and the aneurysm may also be ascertained.