In addition to the physiologic manifestations of atrial fibrillation (stroke, ventricular arrhythmia), patients with postoperative arrhythmias have subjective concerns because of symptoms (palpitations), and prolonged length of stay and hospital cost are significant sources of visceral morbidity to both patients and their physicians. Efforts to terminate this arrhythmia after its initiation are fraught with problems ranging from ineffectiveness to toxicity. Fortunately, a variety of pharmacologic strategies are now available to prevent atrial fibrillation after cardiac surgery. At a minimum, low-dose postoperative beta-adrenergic blockade is valuable for patients who receive these medications preoperatively and may be beneficial in all patients. Moreover, emerging data suggest that prophylaxis with antiarrhythmic compounds can significantly decrease the incidence of atrial fibrillation, length of hospital stay, and cost. Future trials will be focused on evaluating the risks and benefits of the newer prophylactic therapies and defining which subpopulations benefit most from such therapy.