One hundred patients with pulmonary hydatid disease underwent thoractomy and operative removal of the cysts. Of the 60 men and 40 women, most were between 3 and 19 years old. Cough, fever, dyspnea, and chest pain were the prominent symptoms in the majority of cases. Intact hydatid cysts were found in 67 patients and infected or ruptured cysts in 33. The Casoni skin test, Weinberg reaction, and eosinophilia were found to be unreliable diagnostic criteria and therefore were not used routinely in our patients. Roentgenological examination was the most valuable diagnostic aid. A single lobe was affected in 72 patients. Unilateral multiple foci were present in 15 patients and bilateral multiple foci in 13. Cystectomy and capitonnage were the preferred operative procedures in most cases. Pulmonary resection was necessary to only a limited number of patients. We conclude that conservative surgical methods such as cystectomy (with or without capitonnage) are preferable, especially for children, whose residual lung parenchyma has great capacity for expansion. The mortality rate among our 100 patients was 2%; both died of cardiac arrest during operation.