There is controversy as to the possible toxic effects of isobutyl-2-cyanoacrylate (bucrylate) when this substance is used for purposes of therapeutic embolization. Two cases are presented in which cerebral arteriovenous malformations were resected, one 42 days and the other a year after bucrylate embolization. In both, pathological examination revealed a brisk intimal foreign-body giant-cell reaction wherever bucrylate was present in a vessel, along with chronic inflammation in the vessel walls and adjacent brain parenchyma. The findings are discussed in the light of other observations on the histotoxicity of bucrylate.