Due to the increased use of tracheostomy and intermittent positive pressure ventilation, patients with trscheal stenosis have become more frequent. Recently we experienced a patient with tracheal stenosis who was tracheostomized upon admission, but unfortunately the stenotic lesion was located below the end of the tracheostomy tube. The stenotic lesion was l.6cm above the carina, its diameter was 0.5 cm, and the length of the stenotic segment was about 2cm, A3,5 mm(I.D.) endotracheal tube was passed through the stenotic lesion via the tracheostomy site, and high frequency jet ventilation was applied with a swivel connector. Immediately after the start of surgery, CO2retention occurred and the driving gas pressure increased from 4p to 5p psi, the I:E ratio from 1:2 to 1: 3, but the respiration rate (100 bpm) was maintained as before. CO2retention was relieved soon. Following end to end anastomosis a 6. 0 mm(I.D.) cuffed endotracheal tube was intubated orally and inhalation anesthesia using N2O-O2-Halothane was maintained until the surgery was completed.