Publisher Summary This chapter discusses the use of endovascular therapy for treatment of cerebrovascular disease. Recent developments in microcatheter technology have enabled endovascular therapists to penetrate the cerebrovascular circulation with greater accuracy and precision than ever before. Improved access has facilitated rapid and safe delivery of liquid adhesives (histoacryl) into the nidus of arteriovenous malformations using flow directed catheters. Endovascular therapy has been used to treat atherosclerotic stenosis of the cervical carotid bifurcation. This therapy may offer an alternative to carotid endarterectomy. Most centers reserve endovascular therapy for patients who have severe comorbid illness or who have surgically inaccessible aneurysms. Partial or complete coil occlusion of a freshly ruptured aneurysm may prevent early rebleeding. The treatment of symptomatic cerebral vasospasm has been facilitated by endovascular techniques. If clinical improvement is not realized within hours after initiation of hypervolemic hyperdynamic therapy, endovascular therapy may be employed.