This report concerns a child who developed left ; Iung collapse during induction of anesthesia for suture ligation of patent ductus arteriosus. Acute massive collapse of a lobe, a whole lung or even both lungs in the space of a few minutes without apparent cause is said to be a rare elinical entity. Clinically this condition is manifested by difficulty in breathing or in inflation of the lung. On auscultation, there may be rhonchi or no sound of any air entry into the lung. If unrelieved, this condition will progress, with hypoxia and cardiac arrest. "We observed that the affected lung expanded during inflation with very high pressure ventilation, and then the collapsed lung was smoothly inflated after suture ligation of patent ductua arteriosus without any specific management. It appears that the development of lung collapse is not through the wrong choice of agents or technics of anesthesia, but from failure to appreciate the hemodynamics of ductus arteriosus or unknown factors. We could not find a definite mechanism of lung collapse, but there are contributing factors including compression of a main brobchus, bronchial secretion, decrease of surfactant and others. The operation was successful and she recovered satisfactorily.