Brengelmann GL, Johnson JM, Hong PA. J Appl Physiol 1979 Sep;47(3):638-42. Esophageal temperature (Tes) varies with depth of insertion. Characteristic features of the esophageal electrocardiogram (ECG) can be used to place probes in the region where the esophagus is between the aorta and the left atrium. This describes a suitable catheter for recording of Tes and ECG and how features of the electrical activity of the atria may be used to place the probe tip. Records of Tes versus depth obtained during heating of four human subjects are included. The technique eliminates the need for radiographic verification of probe position. It could readily be employed in clinical situations with the advantage of having both a central temperature and an electrocardiogram available from a simple, readily inserted, and readily tolerated catheter.