We studied seven patients with left cerebral atriovenous malformation (AVM) with superselective arterial injection of anesthetics during angiography to determine whether there was translocation of some language functions to other regions in the ispilateral hemisphere. All patients were right handed. With a catheter inserted into each target vessel, patients underwent aphasia examination in an A-B-A design: (A) baseline, no anesthetic; (B) 1 minute after anesthetic injection; and (A) 12 minutes after injection (when its effects had dissipated). The results showed that six of seven patients had no significant aphasia at baseline or 12 minutes after anesthetic injection. One patient had a mild conduction aphasia at baseline and after anesthetic effects had dissipated. In the six patients with temporoparietal AVM, anesthetic injections into vessels in the lower division of the middle cerebral artery (MCA) not feeding the AVM (e.g., the left angular artery) produced a wide range of language function-from conduction aphasia to dense Wernicke's syndromes. When upper division MCA vessels were injected (e.g., the prefrontal branch), all developed a major aphasic disorder with significant comprehension defects. A seventh patient with a frontal opercular AVM had a mild anemia, semantic paraphasias, and decreased word-list generation when the prefrontal branch was injected. Her comprehension, however, was intact. These data show that patients with posterior cerebral AVM can show language abnormalities where such deficits are not typically seen after acute brain injury. These findings support a posterior-to-anterior extension of some language skills under conditions of brain disease.