During the period 1994-1998, three patients with bilateral hydatid cysts of the lung (HCL) underwent operative removal of the cysts. In three of the six lungs operated upon the conventional technique was used: after removal of the cyst and suture closure of bronchial leaks, the chest was closed with an intercostal drainage tube. Two of these patients developed bronchopleural fistulae requiring rethoracotomy and prolonged hospital stays. The other three lungs were operated upon using the pneumonostomy technique: after excision of the cyst a separate catheter is fixed within the residual lung cavity and brought out through the adjacent chest wall, effectively marsupialising the residual cavity to the atmosphere. All these patients had an uneventful postoperative recovery. We conclude that the pneumonostomy technique is a very useful method of treating HCL surgically, especially when the cysts are bilateral and complicated.