Thrombotic occlusion of the left common iliac artery occurred in a 59-year-old man after an anterior and posterior spinal fusion. Preoperatively, the patient was known to have peripheral vascular disease. Symptoms of an L4–5 radiculopathy were noted postoperatively. After an iliac-iliac bypass, the symptoms completely resolved. Retraction of the vessels during the anterior retroperitoneal approach was the presumed cause. To the authors' knowledge, this is the first report of a thrombotic occlusion developing in a patient after an anterior retroperitoneal approach to the lumbar spine. It is their hope that through an increased awareness similar complication will be prevented.