Venous anomalies are not infrequently encountered during aortoiliac reconstruction, because of the complexity of development of the venous system. Retroaortic left renal veins, duplicate inferior vena cava (IVC), and left-sided IVC are occasionally found. Left-sided IVC has been reported with infrarenal aortic aneurysms. We report successful repair of a thoracoabdominal aneurysm in a patient with a left-sided IVC. The embryology and intraoperative management are discussed.