A simple method of measuring the pressure exerted by the cuff of an endotracheal tube on the trachea is described and has been used to measure the pressures exerted by 16 commercially available cuffs on the wall of a model trachea. The Shiley, Portex soft-seal, Kamen-Wilkinson (Bivona Fome) tubes had the lowest tracheal wall pressures. Using this method in vivo the changes in tracheal wall pressure exerted by a low-pressure cuff during percussion and vibration physiotherapy, and when the patient “fights the ventilator”, were recorded.