Av malformations are cerebral abnormalities with a high risk of bleeding. The role of MRI and MR angiography (MRA) for demonstrating these congenital vascular malformations has been studied. It has been shown that MRI/MRA can provide a rapid and certain diagnosis. MRA can demonstrate arteries to the second set of branches beyond the main cerebral vessels. It has the advantage of being able to produce rapidly and non-invasively 3-D images and, unlike conventional angiography, it can be repeated at will. The disadvantage is the limited spacial resolution and the difficulty in distinguishing between arteries and veins.