Among 84 surgically resected arteriovenous malformations (AVMs), four were found to have refractile foreign particles lined by endothelium in the vessel walls. In three cases, this was associated with granuloma formation. The particles were probably introduced during cerebral angiography. They represent a not unusual pathologic finding, are relatively more common in AVMs than in other neurosurgically excised lesions, and may have clinical significance, especially if abundant.