The oesophageal temperature recorded in the anaesthetized and intubated adult depends on the site at which it is taken. The longitudinal variation is greater than the lateral and can be as much as 6°C. The lowest temperatures are found in the upper and middle thirds. Both longitudinal and lateral variations level out in the lower third. The lower fourth of the oesophagus is both the warmest and the most stable. To reach this area, thermocouple leads should be inserted at least 24 cm below the comiculate cartilages.