High frequency jet ventilation (HFJV) has advantage for laryngomicrosurgery that the transit of a small airway tube through the surgical field causes much less interference with surgery. We experienced a case of tension pneumothorax during high frequency jet ventilation. The possible cause of barotrauma in this case was obstruction of gas escape. It is recommened that meticulous care is taken to ensure and adequate pathway for expiration when HFJV is used.