Most iliac arterial aneurysms are extension of aortic atherosclerotic disease. Isolated iliac arterialaneurysm, a rare type of aneurysm, is located deep in the pelvis, does not often produce symptoms, and is dificultto detect clinically. These factors, compounded by its rarity, account for the infrequent diagnosis of isolatedintrenal iliac arterial aneurysm before a catastrophic complication such as rupture. We experienced two recentcases of isolated bilateral iliac arterial aneurysms which were diagnosed and managed before and after rupturerespectively, and showed wide differences -survive and expire- in their postoperative prognoses.