Most iliac arterial aneurysms are extension of aortic atherosclerotic disease. Isolated iliac arterial aneurysm, a rare type of aneurysm, is located deep in the pelvis, account for the infrequent diagnosis of isolated internal iliac arterial aneurysm before a catastrophic complication such as rupture. We experienced two recent cases of isolated bilateral iliac arterial aneurysms which were diagnosed and managed before and after rupture respectively, and showed wide differences - survive ad expire - in their postoperative prognoses.