Transesophageal cardioversion was applied in 277 patients 296 times for arrest of cardiac arrhythmia. Paroxysmal fibrillation and flutter of the atria, and paroxysmal tachycardia were arrested in all cases, chronic atrial fibrillation in 92.4% and chronic irregular atrial flutter in 94.1% of cases. In the group of patients where transthoracic cardioversion at a voltage of 7 kV proved ineffective, the sinus rhythm was restored in 76.5% of cases with atrial fibrillation and 84.2% of cases with irregular atrial flutter when one of the electrodes was introduced into the esophagus. The mean defibrillating voltage in transesophageal cardioversion for chronic atrial fibrillation was by 53.8% lower than that in transthoracic cardioversion. The design of the esophageal electrode proposed provides for the continous recording of the ECG in the esophageal lead for the purpose of determining the optimum position of the electrode and identifying the character of disorders in the cardiac rhythm more precisely.