With the widespread availability of non-invasive imaging of the brain in an aging population, we are increasingly confronted with the problem of the incidental discovery of unruptured aneurysms. The management of these patients remains controversial. Endovascular treatment can prevent rupture, but involves immediate risks. Furthermore, successful treatment does not eliminate all risk of rupture. The safety and efficacy of endovascular treatment of unruptured aneurysms remain undetermined. Hence the balance of the risks and benefits is uncertain. A randomized trial is needed to assess the potential benefits of endovascular management of unruptured aneurysms. TEAM (Trial on Endovascular Aneurysm Management) is a randomized trial comparing endovascular treatment versus conservative management of unruptured aneurysms. TEAM aims to recruit 2002 patients in 60 centers throughout the world over a 3-year period and to follow all patients for 10 years. The primary outcome is to verify if the clinical outcome (morbidity/mortality (modified Rankin scale > 2) related to the aneurysm or its treatment) can be improved from 8% to 4%. The study is funded by the Canadian Institutes of Health Research.