Thirteen years' experience with the surgical treatment of hydatid cystic disease of the lung is analyzed. An unselected series of 149 consecutive patients is reviewed. The preoperative diagnosis was exact in 98% of the cases, our conclusions being based primarily upon radiologic findings. The procedures used were puncture-aspiration with the trocar-suction cup in 139 cases, enucleation in four, wedge resection in two, segmentectomy in one, and lobectomy in three. In 19 cases, capitonnage of the residual cavity was performed: in the rest, partial resection of the pericystic membrane was performed, everting the cavity toward the pleura and using a high negative pressure vacuum through the thoracic drainage tubes. The early mortality was 1%. The persistence of a residual cavity was five times more frequent in those cases in which capitonnage was performed. The recurrence rate of the disease after an average follow-up of 37.5 months per patient was 0% in patients with an unruptured cyst and 9.3% in those in whom the cyst had ruptured prior to operation. As a whole, the percentage of morbidity and mortality in the short and long terms in this series is superior to those quoted in the literature, where other procedures were used.