Objective: To analyze the 1070 catheter-based angiograms performed on patients undergoing carotid artery stenting (CAS) in the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST). Background CAS may be useful as an alternative to carotid endarterectomy in selected patients with symptomatic and asymptomatic carotid artery disease. The angiographic predictors of stroke following CAS have been incompletely described. Design/Methods: Of the 1070 CAS patients, 43 (4%) experienced periprocedural stroke. Angiograms were reviewed before and after CAS. Reviews were blinded to outcomes. Strokes were adjudicated by a committee blinded to results of angiography. The view showing the most severe stenosis was selected. Extreme tortuosity was defined as 2 severe bends >90 degrees (maximum angulation/20 mm segment) beyond the target lesion, sequential lesions as lesions separated by ≥10 mm, and narrow mouth ulcer as a discrete area of contrast extension beyond the normal arterial lumen with a narrow inlet into the ulceration. Results: The internal carotid artery mean reference diameter was 4.2 ± 0.8 mm, the minimal mean lumen diameter was 1.1 ± 0.6 mm, and the baseline mean % diameter stenosis was 74.1 ± 11.6%. There were no differences in vessel size or severity of the stenosis in patients with and without stroke. Morphologic predictors significantly related to the risk of subsequent stroke were lesion length (p=0.009), sequential lesions (p=0.007), severe distal tortuosity (p=0.025), and narrow mouth ulcer (p=0.05). Calcification, lesion eccentricity, baseline flow, and distance from the bifurcation were not predictive of periprocedural stroke (p > 0.05). Conclusions: In CREST, four angiographic variables were found to increase risk for stroke during and within 30 days after CAS: severe distal tortuosity, sequential lesions, lesion length > 20 mm, and narrow mouth ulcer. Angiographic characteristics beyond percent stenosis may help in patient selection in terms of best revascularization option. Supported by: The National Institute of Neurological Disorders and Stroke (NINDS) and the NIH (R01 NS 038384) and by supplemental funding from Abbott Vascular Solutions (formerly Guidant). Disclosure: Dr.Roubin has received royalty payments from Abbott Vascular and Cook Inc. Dr. Popma has received personal compensation for activities with Boston Scientific as a consultant.Dr. Popma has received research support from Boston Scientific, Cordis, Abbott Vascular, and Medtronic. Dr. Almonacid has nothing to disclose. Dr. Morrish has nothing to disclose. Dr. Katzen has received personal compensation for activities with Boston Scientific, W.L. Gore, and Medtronic as a consultant and particpant on an advisory board. Dr. Chakhtoura has nothing to disclose. Dr. Lal has nothing to disclose. Dr. Voeks has nothing to disclose. Dr. Meschia has nothing to disclose. Dr. Brott has received personal compensation for activities with 3D Communications.