Giant traumatic intracranial aneurysms are rare, and thus their incidence and clinical behavior are poorly understood. In most cases, traumatic aneurysms develop and become symptomatic within months following injury. The authors present the case of a 46-year-old war veteran, in whom a giant internal carotid artery aneurysm developed as a result of a penetrating cranial shrapnel injury sustained 25 years earlier during the Vietnam war. The aneurysm had not been evident on previous imaging studies. At surgery, a piece of shrapnel was found embedded in the dome of the aneurysm. The presentation, diagnosis, management, and treatment options related to this lesion are discussed.