A Randomized Trial of Unruptured Brain AVMs is a multidisciplinary international randomized controlled clinical trial including 800 adult patients with the diagnosis of an unruptured brain AVM. Patients willing to participate are randomly assigned to either best possible invasive therapy (endovascular, neurosurgical, and/or radiation therapy) or medical management without intervention. The study protocol does not modify any routine treatment strategies in either arm. Patients will be followed for a minimum of 5 years and a maximum of 10 years from randomization.The primary outcome measure is the composite endpoint of death from any cause or stroke (clinically symptomatic hemorrhage or infarction confirmed by imaging). The secondary outcome measure is long-term clinical status by Rankin Scale, NIHSS, SF-36, and EuroQol.Patient enrollment was successfully started in 2007. Participating sites currently include multidisciplinary treatment centers in North and South America, Australasia, and Europe (including Australia, Austria, Brazil, Canada, Finland, France, Germany, Italy, Netherlands, Spain, South Korea, Switzerland, UK, and the USA).The trial is sponsored and monitored by the US NIH/NINDS (NCT00389181).