To determine whether the filling of tracheal tube cuffs with saline would decrease their combustibility during laser surgery, 20 polyvinylchloride tracheal tubes were studied. The cuffed end of each tracheal tube was inserted into the neck of an empty flask, and the tube and flask were flushed with oxygen for 5 min before cuff inflation. Ten tracheal tubes had their cuffs inflated with air, and 10 were inflated with saline. A Lasersonics LS880 CO2 laser, set to 5 W for five of each of the two types of filled cuffs and to 40 W for the other pair of five tubes, was fired continuously at the cuffs for up to 1 min. No combustion occurred at the 5-W setting. The times to cuff perforation when the laser was set at 5 W were (mean +/- SD) 1.00 +/- 0.83 and 4.21 +/- 3.91 s for the air- and saline-filled cuffs, respectively, a difference that was not statistically significant. The time to deflation of the saline-filled cuff (104.6 +/- 67.5 s) was, however, significantly longer than that of the air-filled cuff (2.59 +/- 1.97 s). When the tracheal tube cuffs were exposed to 40-W laser radiation, the cuff and adjacent tube shaft ignited in all cases when the cuffs were inflated with air, but only in one of five cases when the cuffs were filled with saline (P less than 0.05). The filling of tracheal tube cuffs with saline provides simple, moderately effective partial protection of the cuff of endotracheal tubes during CO2 laser airway surgery.