Chylothorax is not a common condition. According to Brescia1it was first described by Bartolet in 1633. Jahsman2in a review of the literature extending up to 1942 was able to find only 102 cases. He reported 3 additional cases, bringing the total number to 105. The following are the classifications of chylothorax: (1) traumatic; (2) obstructive or nontraumatic: (a) intraductile obstruction due to new growth, filaria or Hodgkin's disease, and (b) extraductile obstruction due to mediastinal tumors, tuberculous glands or aortic aneurysm; (3) associated diseases such as thrombosis of the subclavian vein, and (4) spontaneous. The presence of a chylothorax is obvious when the pleura is perforated, as in the traumatic cases, but is difficult to explain when it is intact, as in the obstructive cases. The flow through the thoracic duct is only 4 mm. per second, and the pressure at its exit into the vein