Transesophageal atrial stimulation was applied in 56 patients to terminate atrial flutter. Extrastimulation and atrial burst techniques were applied using programmable stimulator (Medtronic 5328) and hexapolar esophageal electrode catheters. Thirty patients were randomized to receive digoxin pretreatment (group A), and 26 patients were randomized to receive procainamide pretreatment (group B). Efficacy of each pretreatment was evaluated by observing the change in the rhythm. In group A, transesophageal pacemaker therapy successfully converted atrial flutter to sinus rhythm in 13 patients and to atrial fibrillation in 14 patients, whereas the arrhythmia remained unchanged in the 3 remaining patients in the digitalized group. In group B, after procainamide pretreatment, sinus rhythm appeared in 19 and atrial fibrillation in 5, and no change was observed in the remaining 2 patients. Procainamide is more efficacious than digoxin (P< 0.05) in facilitating cardioversion by transesophageal stimulation.