Objective To review the effects of preventive management during the operation for post-operative chylothorax in patients with lung cancer of state Ⅲ. Methods Total 425 patients underwent pulmonary resection (at least lobectomy) and systematic mediastinal lymph node dissection for lung cancer of state Ⅲ from January 1998 to June 2005. Took some especial management during the operation to prevent post-operative chylothorax in 132 patients after March 2004. According to the surgical procedure,all patients were divided into preventive group and non-preventive group. Results There were 14 patients (4.8%) with post-operative chylothorax in the group of inchoate 293 patients before March 2004. Only 1 patient (0.07%) among 132 patients who underwent treatment for chylothorax during the operation after March 2004 had post-operative chylothorax (P