A case is described showing the following rare combination of anomalies: (a) the thoracic duct terminating on the right side at the junction of the internal jugular and subclavian veins; (b) the right subclavian artery arising as the last branch of the aortic arch, beyond the left subclavian artery, and passing behind the oesophagus on its way to the upper limb; and (c) the right and left common carotid arteries arising by a common stem ('truncus bicaroticus') from the aortic arch. The literature on the subject is reviewed and the embryological basis for the development of these variations is discussed briefly. It is suggested that special attention be directed to the course of the thoracic duct whenever an anomaly of the branches of the aortic arch is observed.Marked variations in the course of the thoracic duct, including its termination at or near the junction of the internal jugular and subclavian veins2 on the right side instead of on the left, are well documented in the literature. With the development of modern thoracic surgery, and particularly that of the thoracic duct itself, there has been renewed interest in the anatomy of this structure and recent descriptions of variations in its pathway have appeared (e.g., Griaznova, 1957;Kausel, Reeve, Stein, Alley, and Stranahan, 1957;Jdanov, 1959;Lachapele, Hughes, and Lagarde, 1964).It is our purpose in the present report to describe an unusual case in which a thoracic duct terminating at the right venous angle was associated with an aberrant, retro-oesophageal right subclavian artery and a truncus bicaroticus, i.e., right and left common carotid arteries arising by a common stem from the aortic arch. Very few instances of this combination of anomalies have been described.These findings may be of practical importance in surgery of the thorax and in the interpretation of radiographs of the vessels in the region under consideration. The embryological basis for the development of these variations may also be of interest. The anomalies were found in an adult dissecting-room cadaver. From the top of the aortic arch (Figs 1 and 4), in front and somewhat to the left of-the trachea, there arose a short, broad trunk, the 'truncus bicaroticus' (Swalowsky, 1888), which ascended vertically for approximately 1'5 cm. and divided into the two common carotid arteries: the right, which crossed the anterior surface of the trachea in a direction upwards and to the right, and the left, running upwards and to the left. Both these arteries then continued into the neck, following their normal course. The left subclavian artery arose from the aortic arch immediately to the left of and somewhat behind the truncus bicaroticus; this vessel then passed upwards and to the left in its normal course towards the left upper limb.The right subclavian artery originated from the aortic arch 1'5 cm. beyond the left subclavian artery, immediately opposite the site of attachment of the ligamentum arteriosum (Figs 1-4). It then passed posteriorly, upwards and to the right between the oesophagus an...