Supraventricular arrhythmias continue to complicate the postoperative course of patients following coronary artery bypass grafting. In a randomized, open, controlled trial we assessed the value of two different beta-blocking agents in the prevention and treatment of these arrhythmias. Of 151 consecutive patients undergoing coronary artery surgery, 39 were treated with metoprolol and 41 were treated with sotalol (a beta blocker with class III antiarrhythmic properties). Fifty patients served as a control group and received no prophylactic therapy. Twenty-one patients were eliminated from the study for various reasons, making a final total of 130 in the study group. In the metoprolol group 15.3% of patients developed supraventricular tachycardia SVT after coronary artery surgery, which was significantly less (p less than 0.05) than the incidence observed in the control group. However, in the group of patients receiving sotalol, 2.4% developed SVT (p less than 0.01 compared with the control group). Of 18 patients in the control group who developed SVT after randomization, 10 received sotalol and 4 metoprolol to terminate the arrhythmia. The mean time of termination of SVT after drug administration was 2.4 +/- 1.8 hours for treatment with sotalol and 13.6 +/- 9.8 hours for treatment with metoprolol. We conclude that sotalol significantly reduces the incidence of supraventricular tachycardia in the early period after coronary artery bypass surgery.