The objectives of this study and registry are to offer the best management possible for patients with brain arteriovenous malformations (AVMs) (ruptured or unruptured) in terms of long-term outcomes, despite the presence of uncertainty. Management may include interventional therapy (with endovascular procedures, neurosurgery, or radiotherapy, alone or in combination) or conservative management. The trial has been designed to test a) whether medical management or interventional therapy will reduce the risk of death or debilitating stroke (due to hemorrhage or infarction) by an absolute magnitude of about 15% (over 10 years) for unruptured AVMs (from 30% to 15%); and, b) to test if endovascular treatment can improve the safety and efficacy of surgery or radiation therapy by at least 10% (80% to 90%). As for the nested trial on the role of embolization in the treatment of Brain AVMs by other means: the pre-surgical or pre-radiosurgery embolization of cerebral AVMs can decrease the number of treatment failures from 20% to 10%. In addition,embolization of cerebral AVMs can be accomplished with an acceptable risk, defined as permanent disabling neurological complications of 8%.