Intimomedial degeneration is a rare and poorly understood vascular disorder involving the circumferential deposition of large amounts of mucoid material within the intima and media of the arterial wall, causing weakening that results in aneurysm formation of the involved segment. The cause of the disease is unknown at this time. The authors describe the endovascular treatment of a large symptomatic superior gluteal artery aneurysm in a patient with multiple arterial aneurysms and the histologic diagnosis of intimomedial mucoid degeneration. In addition, they perform a review of the literature on this unusual vasculopathy.