Six hundred and one patients who were about to undergo non-emergent open-heart surgery were randomized to receive oral amiodarone (10 mg/kg/day) or its matching placebo from six days before surgery through 6 days after surgery. The major outcome tracked was the incidence of more than 5 minutes of an atrial tachyarrhythmia that prompted therapy by the sixth post-operative day. Safety was assessed by the incidence of dosage reduction of blinded therapy, non-fatal post-operative complications, and in-hospital mortality. The randomization scheme was stratified to permit separate analysis of patients less than versus more than or equal to 65 years of age, patients having coronary artery bypass surgery alone versus those having valve surgery with or without concomitant bypass surgery, and patients also receiving versus not also receiving concomitant therapy with a beta-blocker medication.