Atrial fibrillation is the most frequently occurring cardiac arrhythmia, with 1.0-1.5 million cases annually. It is a risk factor for congestive heart failure, and stroke, 75,000 cases of the latter occurring annually in patients with atrial fibrillation. The safety of the most widely used antiarrhythmic agent for this group of patients, quinidine, has been called into question. This study seeks to determine whether two other agents, amiodarone and sotalol, are safe and effective treatments for patients with atrial fibrillation.