Transesophageal atrial pacing has been widely used for studies in cardiac electrophysiology as well as for other cardiac studies in which acceleration of heart rate cannot be achieved or closely controlled with exercise. However, the theoretical basis of the technique and the possibility that it may produce electrical burn injury to the esophagus have not been well-described in the electrocardiographic literature. This review examines the current density produced by an esophageal electrode and compares it with that produced by an intra-atrial catheter electrode. It also presents data on the extent of esophageal burning produced by transesophageal pacing in dogs.