Acute lung edema during anesthesia and operation is not common. We experienced a case of 7 year-old boy who developed acute lung edema during open reduction for his fractured lateral condyle of right humerus under general anesthesia with enflurane. In his previous history, we couldn't detect any abnormal finding that could induce lung edema intraoperatively. Preoperative routine laboratory findings and chest x-ray findings were within normal ranges. In the end of operation, increased airway resistance and sudden facial cyanosis were detected and he received immediate, careful supportive respiratory management. He improved from severe lung edema, but hypoxic brain damage and motor dysfunction resulted. We couldn't find any evidence that he had heart failure, hypoalbuminemia, sepsis, severe trauma, fluid overloading. Authors couldn't get exact causes of acute lung edema in this case.