Variations in the site and course of the inferior vena cava (IVC), although relatively infrequent, can have important surgical implications, especially during surgery for abdominal aortic aneurysm. We report two cases of left-sided IVC encountered during aneurysmectomy. In both cases, the anomaly was not detected during preoperative ultrasound examination, but was identified by CT scan in one case. Careful mobilization of the IVC and left iliac vein allow retraction of the IVC to the right, after which the aneurysm can be approached in the usual manner.