Nineteen patients with large cortical or deep seated cerebral arteriovenous malformation (AVM) were treated with intraoperative embolization using bucrylate (isobutyl-2-cyanoacrylate, IBC). In three cases of medium-sized AVM, the procedure was followed by a total excision of the lesion during the same operation. The results were excellent. In one case a hematoma and brain swelling following embolization necessitated total removal immediately afterwards. In eight patients embolization was carried out in two or three stages, to achieve a gradual obliteration of the shunt and to diminish the risk of postoperative brain swelling. Nevertheless, in three of these patients, postoperative hemiplegia was seen, which, however, improved considerably over a 1-2 year period. Complete occlusion of the shunt was obtained in only two patients. Seven patients underwent single-stage embolization, which resulted in partial obliteration of the AVM in six of them. In two of these, this treatment had been proposed for the accompanying symptoms of seizures and ischemic attacks. In all but one case the epileptic seizures decreased or disappeared completely after embolization. One patient suffered intracerebral bleeding three months after partial obliteration. Mortality was zero. It is argued that an alteration of the cerebral circulation with subsequent hyperemia is the most important sequela of rapid obliteration of large AVMs. Some details concerning the structure of cerebral AVMs are discussed.