In laser laryngomicrosurgery, saline is injected into the endotracheal tube cuff to prevent airway fire. Utilizing regression analyses, we investigated the relation between the saline volume required to obtain optimal intracuff pressure and tracheal diameters in patients undergoing laser laryngomicrosurgery as well as in model tracheas. Although excellent linear correlations were found between the saline volume and the diameter of model tracheas, no significant linear or non-linear correlation was found between the saline volume and the patient's tracheal diameter. In the model tracheas, a rate of rise in the intracuff pressure caused by increments in the injected volume was far steeper when saline was injected into the cuff than when air was injected into the cuff. Addition of only 0.2 ml saline could result in large (> 50 mmHg) increases in the intracuff pressure. Also in patients, addition of 1 ml could result in notable (> 50 mmHg) increases in the intracuff pressure. These results suggest that the saline volume necessary to obtain optimal intracuff pressure is difficult to be predicted from the patient's tracheal diameter, and that slight increases in the saline volume may cause excessive increases in the intracuff pressure. The intracuff pressure should be tightly monitored in patients undergoing laser laryngomicrosurgery.