Gorham-Stout syndrome is a rare disease and most often recognized in children and young adults. Chylothorax is a serious complication of Gorham-Stout syndrome. The treatment of either Gorham-Stout syndrome or chylothorax is still a dilemma. We described a 9-year-old girl with Gorham-Stout syndrome and chylothorax who was admitted to our hospital because of dyspnea, orthopnea, and bone pain, and treated with interferon alpha-2b. Pediatr Pulmonol. 2009; 44:613-615. (C) 2009 Wiley-Liss, Inc.