When the tracheal tube with a high-volume, low-pressure cuff is used, the pressure exerted by the cuff on the tracheal wall is similar to the intracuff pressure, and the pressure is claimed to be lower than the capillary perfusion pressure; however, it is not known if this is the case when a high airway pressure is required. In a randomized, cross-over design, we studied 61 patients (31 men) and measured the intracuff pressures of the tracheal tube at various airway pressures. While the lungs were inflated at five different airway pressures in turn (10, 15, 20, 25 and 30 cm H2O), the cuff of the tracheal tube was inflated with air until it prevented an airleak ('just-seal' pressure). Intracuff pressures [median (range)] at airway pressures of 10, 15, 20, 25 and 30 cm H2O were 8 (0-20), 15 (4-20), 22 (6-32), 26 (11-52) and 31 (16-54) cm H2O, respectively, for men and 6 (0-20), 11 (0-20), 15 (0-24), 21 (0-32) and 25 (1-41) cm H2O, respectively, for women. Therefore, we conclude that the pressure exerted by the cuff of the tracheal tube on the tracheal wall is unlikely to exceed the capillary perfusion pressure (arbitrarily defined as 25 mmHg or 34 cm H2O) when the airway pressure is 25 cm H2O or less, but it may exceed the capillary perfusion pressure when the airway pressure is greater than 25 cm H2O.