Genetic analysis of the familials of patients with arteriovenous malformation (AVM) has a significant potential to reveal the etiology of this disease, although neither the detailed etiology nor pathogenesis of AVM has been fully elucidated to date. While a history of AVM is apparent in 2% of stroke patients, familial occurrence of AVM is very rare. We describe an interesting familial case of AVM. This also represents a rare pattern of familial occurrence in that patients are not likely hereditary hemorrhagic telangiectasia (HHT). There is a possibility that such familial AVMs are associated with unknown genes other than HHT genes.