A 70-year-old woman presented with symptoms of progressive cerebellar dysfunction due to mass effect from a giant, expanding, posterior fossa aneurysm arising from the distal vertebral artery. The aneurysm contained thrombus and had a broad-based neck. From a transfemoral approach, with the patient under local anesthesia, a 2.2 French microcatheter was guided through the vertebral artery and placed directly into the aneurysm. Six 5 x 15-mm platinum microcoils were deposited into the residual lumen of the aneurysm, resulting in complete thrombosis with obliteration of the aneurysm and preservation of the parent artery. Endovascular coil embolization therapy by interventional neurovascular techniques may provide a therapeutic alternative in the management of surgically difficult symptomatic intracranial aneurysms.