This study evaluates the use of MR angiography in the diagnosis of vertebrobasilar stroke. The MRI/MR angiography and clinical presentation of 50 unselected adult patients who presented with ischemic symptoms in the vertebrobasilar territory (10 TIAs, 40 strokes) were prospectively evaluated. Conventional T1 and T2-spin echo sequences were obtained for evaluation of the brain parenchyma, with gadolinium injection in 41 cases and 3D time-of-flight MR angiography in all patients. Data were reconstructed with a maximal intensity projection algorithm and displayed in 3D. Arterial and parenchymal lesions and clinical data were correlated. MR angiography showed intracranial vertebrobasilar lesions in 30 patients (5 stenosis or occlusion of a vertebral artery, 17 stenosis or occlusion of the basilar artery, 6 stenosis of arterial branches of the basilar artery, 10 dolichoectasia of the basilar artery). 7 patients had multiple lesions. Recognized etiologies of the strokes were: 23 vertebrobasilar lesions, 16 nonvertebrobasilar causes, 6 mixed (vertebrobasilar and associated alternative causes) cases, while 5 cases had no recognized cause of stroke. Our study demonstrates a high incidence of intracranial arterial lesions in patients suffering from vertebrobasilar stroke and suggests that MRA can help in a noninvasive way to determine the origin of vertebrobasilar strokes.