The superior intercostal veins define the pleural reflections of the caudad extent of the posterior junction line. They are paired structures which drain the first three intercostal spaces and join the azygous on the right and the accessory hemiazygous on the left. Because of their location posterior and lateral to the esophagus and trachea, their pleural reflections may be altered early in the course of a focal nodal disease of the posterior mediastinum.