During anesthesia increase of the endotracheal cuff pressure might be caused by anesthetic gases used, especially nitrous oxide (N2O), which easily diffuses into the cuff. In 1983, Brandt developed a blocking system which is called Rediffusion System. The principle of Rediffusion System is to make use of an enlarged pilot balloon to facilitate the removal of nitrous oxide which has diffused into the cuff during anesthesia. This study was designed to test and verify the function of Brandt tube's Rediffusion System during anesthesia using nitrous oxide as an anesthetic. Twenty four patients (age 19-82 yr; ASA physical status I-III) who underwent surgery under general anesthesia were allocated into three groups. For endotracheal intubation, in group I (n = 11) and group II (n = 5), Mallinckrodt Brandt tubes respective of internal diameter (ID) = 7 mm and ID = 8 mm were used, and in group III (n = 8) Portex Blue-line tubes with ID = 7 mm was used. Anesthesia was maintained with N2O, isoflurane, and oxygen and the FiN2O was kept around 50%. The cuff pressure was measured at the intervals of 30 min for 3 h. There were no significant differences of initial cuff volumes between group I and group II, but the initial cuff volumes of Portex blue-line tube were significantly larger than Brandt tubes at desired pressure level. Cuff pressures increased as the duration of anesthesia lengthened in all types of endotracheal tubes.(ABSTRACT TRUNCATED AT 250 WORDS)