Ignition or combustion of the endotracheal tube during CO2 laser microlaryngo surgery may cause fatal lung disorders. We undertook an experiment on ignition and combustion of endotracheal tubes by CO2 laser beam and came to the following conclusions: (a) the silicon endotracheal tube was nonflammable; (b) the spiral endotracheal tube was also nonflammable; (c) a pulse wave was recommended and 3-second intervals were necessary; (d) four sheets of moist gauze were necessary to prevent cuff trouble, and (e) it was advisable to set the O2 concentration below 25 % when using the silicon endotracheal tube.