To value changes of endotracheal tube cuff pressure during anaesthesia with N2O, using standard tubes or Brandt-system tubes. Endotracheal cuff pressure during anaesthesia in three groups of patients has been monitored: Group 1 (n. 41): endotracheal tube with low-pressure cuff using N2O/O2 (2:1 or 1:1); Group 2 (n. 55): Brandt's double cuff-tubes using N2O/O2 (2:1 or 1:1); Group 3 (n. 20-control group): tubes with low-pressure cuff using O2/air. Values of pressure (M +/- DS: p < 0.05) have been compared with ANOVA, Bonferroni's method (p < 0.017). Brandt's double cuff-tubes (G2) succeed in avoiding uncontrolled increase of cuff-pressure during anaesthesia with N2O. Standard low-pressure tubes (G1) shown increase of cuff pressure during anaesthesia with N2O which is absent using no N2O (G3).