A 50-yr-old man with the nephrotic syndrome developed a chylothorax that was shown to be due to transdiaphragmatic movement of chylous ascites. Because a significant number of patients with nephrotic syndrome have been reported to have chylous ascites, the possibility that chylothorax is due to movement of chylous ascites into the pleural space should be considered prior to surgical intervention directed toward repair of the thoracic duct.