The case of a 65-year-old man who had partial left third nerve palsy is reported. Radiographic examination disclosed a completely thrombosed giant suprasellar aneurysm. Although an angiogram appeared to indicate that his aneurysm arose from the distal basilar artery, he was also noted to have an unusual and ectatic distal internal carotid artery on the left side, and this was also felt to be a potential source of the aneurysm. Operative exploration was performed and confirmed the basilar artery as the sight of origin, and definitive therapy was deferred. The patient's progress was monitored, and for 3 years his neurological course was stable and there was no change in his radiographic abnormalities. During the 6 months following this period, the patient developed signs and symptoms of progressing hydrocephalus and was found to have significant enlargement of his still completely thrombosed giant aneurysm. This complicated case highlights the controversy regarding the management of this difficult condition, particularly with regard to endovascular therapies, and also provides insight into the evolution of this dynamic disease process.