Ten cases of arteriovenous malformations located in critical areas of the cerebrum, i.e., motor and speech areas, the insular cortex, the corpus callosum, and the basal ganglia, were treated surgically by radical removal of the lesion. In four of the cases a neurologic examination before surgery was negative; five cases exhibited only mild hemiparesis or dysphasia; only one exhibited hemiplegia and stupor. There were no postoperative deaths and a residual permanent deficit was noted in only one patient. Postoperative control angiograms failed to show any filling of the arteriovenous malformations in any of the cases. Recovery of the ability to work was achieved in all of the patients. The operating microscope and controlled hypotension made possible a precise resection at the edges of the lesion, and damage to surrounding important cerebral structures was thus avoided. Based on these results, microsurgery should be considered as an elective therapy for these kinds of arteriovenous malformations, even when preoperative symptoms are minimal.