In the cadaver of a Japanese 79 year-old man a retroesophageal right subclavian artery was observed to be derived from the arch of the aorta slightly distal and dorsal to the left subclavian artery. Its origin formed Kommerell's arterial diverticulum (50 mm in circumference), and it passed between the esophagus and the vertebral column and continued to the right to become the axillary artery. No right recurrent laryngeal nerve was observed. There was a right ansa subclavia around the subclavian artery. Although this anomaly is relatively rare, it is important as a cause of dysphagia lusoria.