Chylothorax is readily diagnosed from the characteristic qualities of the effusion. Treatment should initially be conservative, consisting of multiple aspirations followed, if necessary, by suction drainage. Approximately half of the patients will not respond to these measures, and direct ligation and division of the duct is necessary for cure. This operation is most readily carried out through the right chest, the thoracic duct being ligated just above the diaphragm. In cases in which the duct is surrounded by tumor, radiotherapy to the mediastinum is often successful in controlling the reaccumulation of chyle, but irradiation is generally not recommended until after a tissue diagnosis has been made by thoracotomy. Nutritional problems are often concomitants of chylothorax.