During surgical repair of a descending thoracic aorta aneurysm, one-lung ventilation improves visualization of the surgical field, facilitates surgical resection, and reduces lung trauma. Trauma to the left lung during surgical repair of the descending thoracic aorta is very common, and intrapulmonary hemorrhage can be occurred if both lungs are ventilated. A double lumen tube can isolate and protect the lungs. During one lung ventilation in the lateral decubitus position, hypoxemia can frequently occur and hypoxic damage can result. Selective nondependent lung high frequency jet ventilation was administered using a MERA JET VENTILATOR with FiO2 1.0, driving gas pressure 1kg/cm2, respiration rate 120/min., and an I:E ratio of 1:2. Oxygenation (PaO2 readings were all above 200 torr) was well maintained and PaCO2 values were all within normal limits throughout the operation. Under the left atrial femoral artery bypass with the cardiopulmonary bypass machine without oxygenator, an internal bypass graft with Woven dacron was performed. The patient tolerated the surgery well, and the postoperative course was uneventful except for left vocal cord paralysis.