Although the incidence of cuff induced tracheal damage has been considerably reduced by judicious use of tracheal tubes with large-volume, low-pressure cuffs, aspiration continues to be a major problem. A study was conducted to determine the maximum hydrostatic pressure that can be produced by a column of liquid above the tracheal cuff. The vertical and horizontal distance between the upper central incisor teeth and suprasternal notch was measured in 200 supine adult subjects. The maximum vertical and horizontal distance between the upper central incisor teeth and suprasternal notch was 9 cm and 21 cm respectively. The implication of these findings are discussed and it is suggested that a fixed intracuff pressure in the range of 2.5 to 3kPa should be used to obtain an optimal tracheal seal.