We measured the intracuff pressure of two different tracheal tubes, Portex Profile Soft-Seal Cuff with high N2O gas-barrier property and "high-volume, low-pressure" cuff (Mallincrodt Lo-Contour). Twenty adult patients undergoing elective abdominal surgery, were maintained with total intravenous anesthesia combined with epidural block, and ventilated with oxygen in air (FIO2 = 0.4). Initially, intracuff pressure was adjusted to 25 mmHg with air, and monitored over 180 min. Intracuff pressure of both tubes decreased abruptly to near 20 mmHg within 20 min, and further went down gradually during the observation period. The decrease in intracuff pressure of Portex Profile Soft-Seal Cuff was significantly smaller than that of "high-volume, low-pressure" cuff 150-180 min later. We conclude that to prevent tracheobronchial aspiration during prolonged general anesthesia without N2O, tracheal tube cuff with gas-barrier property may be safer than usual "high-volume, low-pressure" cuff. We recommend to check the intracuff pressure especially during the first 30 min and at intervals of several hours.