This chapter will review the current status of scientific knowledge to support evidence-based medicine guidelines for the endovascular treatment of cerebrovascular disease. Three major areas of cerebrovascular disease will be examined, (1) occlusive cerebrovascular disease, (2) vascular malformations and (3) intracranial aneurysms. Levels of evidence vary in each area and the reasons for this variation as well as the challenges that may limit further investigations are discussed.