Background and Objectives: The nonrecurrent laryngeal nerve(NRLN) is exceedingly rare nerve anomaly that is associated with developmentally aberrant subclavian artery. The presence of NRLN is associated with an increased risk of vocal cord palsy in thyroid surgery. The purpose of this study is to investigate its prevalence, associated vascular anomaly and necessity of recognizing its possibility for prevention of intraoperative nerve damage. Materials and Methods: Between January 2004 and December 2006, 583 thyroidectomy were performed at our hospital. Of these cases, 529 cases(90.7%) were checked preoperative neck CT. Results: Patients with preopreative neck CT, 6 cases show the retroesophageal abberant right subclavian artery that arising directly form the aortic arch. 5 cases of these 6 cases(5/6, 83.3%) and of 583 patients(5/583, 0.8%) performed thyroid surgery were identified NRLN per-operatively. All of them are identified on the right side. There were 4 women and 1 man. In all cases, there were no clinical symptoms. I case was performed only left hemithyroidectomy, so we cannot identified NRLN. No vocal cord palsy was observed. Conclusion: It is possible to predict NRLN from preoperative neck CT. When NRLN is suspected, careful, complete dissection of the nerve is always advocated. These process can reduce the operative morbidity.