Background: Hydatid disease is caused by an infection with the cestode, Echinococcus granulosus and is endmic in Iran. Medical therapy and surgical management are two main treatments. The purpose of this study is to represent our ten-year experience in surgical management of patients with complicated pulmonary hydatid disease including cysts ruptured into the pleural space or bronchi, multiplicity, hemoptysis, large size cysts and coexistence with liver cysts. Materials and Methods: Medical records of 109 patients, who underwent surgery for the treatment of pulmonary hydatid disease in Masih Daneshvari Hospital from December 1995 to October 2005, were reviewed. Among these patients, we selected our study group in accordance with the following criteria: 1) Cyst rupture into the pleural space or bronchi, 2) Occupying more than two third of the hemithorax in radiological studies, 3) Multiple cysts, 4) Massive hemoptysis, and 5) Synchronous pulmonary and liver cysts. Results: Among the 109 patients with pulmonary hydatid cyst, 82 patients (59% male and 41% female) met the above mentioned criteria. The mean age of patients was 31.7 years (range 9-80 yrs). The cyst diameter was determined by radiological imaging. The mean diameter was 6.23 cm, and 13 patients had giant cysts (occupying more than 2/3 width of the hemithorax). In this study group 55 patients had ruptured hydatid cysts, 29 had multiple cysts, 11 had significant hemoptysis and 15 had synchronous pulmonary and liver cysts. All patients had undergone surgery with or without previous medical therapy. Our procedure of choice was thoracotomy, cystectomy and closure of the bronchial openings before irrigating the cavity with silver nitrate (0.5 %) soaked sponge. Pulmonary resection was done in 8 patients due to the irreversible parenchymal damage. Post operative complications occurred in 16 (19%) patients including residual pleural space in 8, broncho-pleural fistula in 2, pleural effusion in 1, pulmonary embolism in 1, osteomyelitis of sternum in 1, laceration of diaphragm in 1, and inability to access the liver hydatid cyst after thoracotomy and post operative pulmonary insufficiency necessitating mechanical ventilation also in 1 patient. One patient died because of sepsis (she had been operated on for combined pulmonary and liver hydatid disease). In the 1 to 60 months follow up period, 2 recurrences occurred. Conclusion: Although post operative complications occurred in 19% of our patients, all were treated by conservative managements. This rate of complications was acceptable among patients with complicated hydatid disease. Our procedure of choice is draining the cyst; closing all the bronchial openings in the pericyst and leaving the pericyst cavity open into the pleural space. (Tanaffos 2007; 6(1): 19-22)