We examined 17 intracranial arteriovenous malformations that were resected after treatment by embolization using bucrylate (isobutyl-2-cyanoacrylate). In nine specimens removed 5 days to 16 months after embolization therapy, a series of pathologic changes was seen, including patchy mural angionecrosis (adjacent to bucrylate fragments) up to six weeks after embolization, the presence of bucrylate in vessel walls and fibromuscular intimal cushions, and the occurrence (after several months) of entirely extravascular bucrylate. Occasional parts of recanalized vascular malformations were identified. Bucrylate was present within arteriovenous malformations as late as 16 months after embolization, although the amount appeared to be diminished. These findings suggest a specific sequence of events in the interaction between bucrylate and mural components within the malformations and may explain some important complications of embolization therapy (e.g., delayed hemorrhage after embolization).