In the maintenance of sinus rhythm group, the choice of drugs was left to the primary treating physician, to be chosen from amiodarone, sotalol, propafenone, flecainide, quinidine, moricizine, disopyramide, procainamide, and combinations of these drugs. Atrioventricular nodal blocking drugs were also administered unless contraindicated. The major substudy for AFFIRM randomized initial drug choice among amiodarone, sotalol, and class I drugs. Prior drugs which were ineffective or poorly tolerated were not repeated. There were various drug exclusions depending on the patient's condition. Patients in the maintenance of sinus rhythm group had multiple cardioversions as needed. If there was treatment failure or intolerance after two or more pharmacologic trials, patients were considered for innovative therapy in Step II. In Step II, two maintenance doses of amiodarone were included, a low dose of 100 to 200 mg/day and a normal dose of 300 to 400 mg/day. Each dose of amiodarone was considered to be a single drug trial, so that patients who received treatment with amiodarone at both dosage levels were considered to have had two drug trials. It was not mandatory that Step II therapies be applied in any individual patient. The following innovative Step II therapies were approved for use in the study: (1) ablation of an atrial focus in patients with type I atrial flutter, if it was clinically documented that the atrial flutter led to atrial fibrillation; (2) atrial pacing alone, with or without documented bradycardia; (3) atrial pacing and antiarrhythmic drugs, with either single site or multiple site atrial pacing; and (4) surgical maze or atrial isolation procedures at selected centers. Catheter-based ablative procedures, such as those attempting to mimic the maze procedure were not approved in this study. Implanted atrial cardioverter defibrillators were also not approved. All therapy was periodically reviewed and subject to modification by the Steering Committee with concurrence by the DSMB and the NHLBI. In the event that sinus rhythm was not maintainable by any treatment, patients crossed over to rate control and anticoagulation.