Twenty-seven patients with epilepsy as the only manifestation of a cerebral AVM were seen at the MNI/MNH from 1973 to 1981. The nine females and eighteen males between the ages of fourteen and fifty-four years (mean 25.2 years) had epilepsy for an average of 3.5 years prior to the diagnosis of AVM. Seven patients had primarily generalized seizures, ten patients had partial seizures with complex symptoms, fourteen patients had partial seizures with elementary symptoms, and thirteen patients had secondarily generalized seizures. Although there was no history of intracranial hemorrhage, seven patients had negative hemispheric signs (hemiatrophy, hemianopia, dysphasia, hemiparesis), two had impaired mentation, and two were ataxic. The EEG, normal in ten cases,showed non-epileptiform activity in six cases, and focal epileptiform activity in eleven cases. Angiographic and/or histological examination revealed eight small (less than 2 cm in diameter) and nineteen large lesions. Fifteen AVMs involved the frontal lobe, ten the temporal lobe five the parietal lobe, and one the occipital lobe. Angiography failed to demonstrate three frontal and three temporal AVMs. Plain CT scanning demonstrated a high or low density lesion without a mass effect in sixteen cases, enlargement of the ipsilateral ventricle or Sylvian fissure in seven cases, and diffuse ventricular enlargement in three cases. CT scanning was performed after the intravenous injection of contrast material in nineteen cases and demonstrated vascular enhancement in fifteen cases and an abnormal blood vessel in six cases. Two angiographically occult AVMs demonstrated vascular enhancement with infusion CT scanning, thereby demonstrating the vascular nature of the lesion where angiography had failed to do so.