Magnetic resonance imaging (MRI) was performed in 15 patients with small to very large supratentorial arteriovenous malformations (AVMs). Unlike non-contrast infused computed tomographic (CT) scanning, MRI demonstrated the AVM in all cases. The nidus had a characteristic honeycomb appearance, and in all cases feeding arteries and deep or superficial draining veins were demonstrated without intervening bone artifact. The relationship of the AVM to surrounding cortical areas, deep nuclei, important white matter tracts, and the ventricular system was well appreciated. These characteristics make MRI useful for the diagnosis of cerebral AVMs and add to the accuracy of systems that grade operability on the basis of the angiographic demonstration of size, location, depth, arterial supply, and venous drainage. In many cases, based on the MRI appearance of the AVM and its relationship to important brain structures, the lesion can be deemed inoperable or unsuitable for other forms of treatment, making angiography unnecessary. Thus, the superior anatomical and morphological resolution of MRI, the lower false-negative rate, and the independence from x-ray and contrast material make MRI more useful than CT scanning for the diagnosis of AVMs and as an aid in the management of specific cases.