Two cases of giant left middle cerebral artery aneurysm presenting with rapidly progressing hemiparesis and aphasia are presented. In both, the computed tomographic scan showed recent intraaneurysmal thrombosis and massive edema and swelling of the cerebral hemisphere. There was no evidence of recent hemorrhage in either case. In both patients, surgical resection of the aneurysm was accomplished, but the outcome was disastrous. The literature is reviewed and the possible mechanisms responsible for brain swelling in these cases are discussed.