Quaal SJ, Phillips B, Howery T, Jadvar H. Prog Cardiovasc Nurs 1989 Jan-Mar;4(1):10-7 . The value of esophageal electrocardiography (ECG) in differential diagnosis of complex arrhythmias has been well known for the past half century. However, until recently, the technique was not widely used primarily because of the patient discomfort associated with esophageal placement of nasogastric tubes containing the ECG electrodes. With the advent of the pill electrode and development of appropriate recording methodology, interest in and use of esophageal electrocardiography has increased dramatically. In this article, the authors review the historic development of the pill electrode, recording technique, and current case studies in which the technique of pill electrode esophageal ECG monitoring facilitated differential diagnosis of complex arrhythmias.