We evaluated three different tracheal tubes, Portex Profile Soft-Seal Cuff (PSSC), Portex Profile Cuff (PC) and Mallincrodt Lo-Contour (LC), when they are used in the artificial trachea and in anesthetized patients. When a cuff was inflated in the artificial trachea, PSSC with a cuff of high N2O gas-barrier property, and PC could achieve air-tight sealing with a smaller amount of injected air, compared with LC. This finding suggests that the inflated cuff-shape and cuff-fold formation are important to block the airway leakage with small volume of air. Either of three tubes was used randomly in thirty adult patients for general anesthesia using nitrous oxide 65%. Intracuff pressures were increased significantly with the passage of time. In PSSC group, however, intracuff pressure was 25 +/- 6 mmHg (mean +/- SD) at two hours, and in other two groups it was between 32 and 48 mmHg. The use of a tracheal tube with gas-barrier cuff is recommended to prevent a high tracheal wall pressure.