A 33-year-old, right-handed man was admitted to our hospital with one episode of generalized convulsion. His general condition and laboratory data were normal. Plain skull films were normal. EEG showed a sharp focus over the left temporal area.     CT scan displayed a low-density area in the left temporal lobe which was enhanced with contrast medium. Angiogram showed an arteriovenous malformation in the left temporal lobe. It was fed by branches of middle cerebral artery and drained through the middle cerebral, Labbé, Trolard and Rolandic veins. Preoperative speech and intelligence tests were normal (SLTA and WAIS).     Amytal test indicated the left cerebral hemisphere to be dominant. AVM was removed from the left posterior superior temporal gyrus. No neurological deficits followed operation, and WAIS and SLTA were normal.     Two years and five months after surgery, EEG-topography was performed under such psychological tasks as animal naming, mental calculation, etc., which showed the left hemisphere to be dominant. These data suggest that the patient's speech center was dominant in the left cerebral hemisphere but had shifted to some other area than the posterior superior temporal gyrus (Wernicke's center).