Of 115 patients with angiographically demonstrated cerebral arteriovenous malformations (AVMs), seizures occurred in 66 (57%), all of whom had supratentorial AVMs. Seizures were the initial manifestations in 36 patients. In 14 patients seizures developed within 30 days of hemorrhage or surgical resection; in 16 others seizures started within 0.5 to 16 years after hemorrhage or resection. Seizures were infrequent in the majority of patients; in only nine (16%) were they incapacitating. Among 46 patients observed from two to 36 years, 23 (50%) were seizure free for a minimum of two years at follow-up. Neurological deficits on examination and previous occurrence of hemorrhage did not adversely affect seizure control. No significant difference was found between the percentage of seizure-free patients in the medical and surgical groups at follow-up. Irrespective of treatment method, seizures starting within 30 days of hemorrhage or resection had the best prognosis.