Between July 1987 and May 1995, 11,315 patients underwent general thoracic surgical procedures at our institution. In 47 of these patients (0.42%), postoperative chylothorax developed. There were 32 men and 15 women with a median age of 65 years (range 21 to 88 years). Initial operation was for esophageal disease in 27 patients, pulmonary disease in 13, mediastinal mass in six, and thoracic aortic aneurysm in one. All patients were initially treated with hyperalimentation, cessation of oral intake, medium chain triglyceride diet, or a combination. Nonoperative therapy was successful in 13 cases (27.7%), and oral intake was resumed a median of 7 days later (range 2 to 15 days). Reoperation was required in the remaining 34 cases. The reoperation rate varied according to the type of initial operation. Twenty-four of the 27 patients (88.9%) who had undergone an esophageal operation required reoperation, versus only five of 13 patients (38.5%) who had undergone pulmonary resection (p < 0.001). Lymphangiography was performed in 16 patients and identified the site of the leak in 13. The thoracic duct was ligated in 32 of the 34 patients who required reoperation (94%). The remaining two patients were treated with mechanical pleurodesis and fibrin glue. Reoperation was successful in 31 of the 34 patients (91.2%). The single death among the 47 patients (2.1%) occurred in the reoperated group. Complications occurred in 18 patients (38.3%). Factors that predicted the need for reoperation were initial esophageal operation and average daily postoperative drainage greater than 1000 ml/day for 7 days. We conclude that postoperative chylothorax is an infrequent complication. Some cases can be managed without operation; however, we recommend early reoperation when drainage is greater than 1000 ml/day or if the chylous fistula occurs after an esophageal operation. The fistula can usually be controlled by ligation of the thoracic duct.