A 48-year-old, right-handed female patient presented tonic generalized seizures followed by left parietal syndrome. At the initial angiography, a filling defect was noted in the proximal segment of the left posterior parietal artery. This arterial narrowing had disappeared and migrated distally at the repeat angiography 16 days later. Histologic examination of the occluded artery found cotton fiber emboli. Cotton fiber embolization during cerebral angiography is a recognized but rather rare complication, 18 such cases having been reported. Pertinent literature on this complication of angiography is reviewed and the mechanism and prevention of such an event are briefly discussed.