Atrial fibrillation is the most common arrhythmia worldwide, is frequently symptomatic, and contributes to significant morbidity and mortality. Providing effective treatment of atrial fibrillation is one of the future tasks of electrophysiology, and is the focus of major research initiatives in the United States and abroad. At the most recent NASPE Scientific Sessions (May 2003), there were 202 abstracts that focused on atrial fibrillation. In addition, several debates and multiple symposium and clinical curriculum dealt with atrial fibrillation. This level of concern and interest regarding atrial fibrillation has increased in the last few years with the advent of curative ablative techniques. Optimal treatment of atrial fibrillation is not currently known, but should become clearer as the results of treatment strategies and basic mechanisms are presented. Current treatment is evolving and will vary according to the patient s symptoms and their risk of thrombo-embolic events. However, there are certain principles of treatment that are generally agreed, including anticoagulation and avoidance of rapid ventricular rates. Anticoagulation is paramount for most patients. Coumadin has been shown in most trials to lower the risk of stroke, and should be considered for all patients. Whether individuals with normal hearts and no risk factors for embolic events benefit coumadin is not entirely clear. Coumadin has been underutilized in many treatment strategies, because of the perceived risk of bleeding or patient and physician desire to avoid the hassles of coumadin management, including special diets, frequent blood draws, and drug interactions. Newer anticoagulation products that are much easier to use are on the horizon and may be available in the near future. Whether rate control and anticoagulation or rhythm control with anti-arrhythmic agents should be utilized has been tested in the AFFIRM trial. The results of this trial suggest that continued anticoagulation is more important in avoidance of embolic events than attempting to maintain sinus rhythm. This trial also demonstrated that neither rate control nor rhythm control is markedly superior and thus individualization of treatment is allowed. Multiple trials have shown that symptoms of atrial fibrillation are not adequate markers of episodes of atrial fibrillation, and thus cannot be relied upon as an indicator of when to discontinue anticoagulation. In the future, more effective and less toxic anti-arrhythmic agents may be marketed. The most exciting development of treatment of atrial fibrillation is curative techniques with catheter ablation. These techniques include focal ablation of atrial tachycardia foci, linear lesions, and isolation of the pulmonary veins. The surgical Maze procedure has shown us that cure of atrial fibrillation is possible. However, this procedure is lengthy, invasive, and not performed by many surgeons at this time. Attempts to reproduce the surgical Maze with percutaneous catheter techniques have shown some success, but the extensive amount of lesions and ablation lines required, the difficulty with obtaining complete block, and the complications have limited this approach. In addition, the cure rates were disappointing low. It has recently become appreciated that very rapid atrial tachycardias, primarily originating in the pulmonary veins, can trigger and sustain atrial fibrillation. First attempts at curing atrial fibrillation involved catheter ablation of these triggers in the pulmonary veins. In this approach, only the tachycardia foci was targeted. Thus, tachycardia must be present in order to map, and inducement with high doses of isoproterenol was frequently necessary. Cures were seen; however, recurrences were common and observed in up to 70% of patients. With the appreciation that recurrent atrial fibrillation in these patients was often secondary to another foci in another pulmonary vein, the concept of pulmonary vein isolation was born, and is currently the generally performed technique in the treatment of atrial fibrillation. Atrial tissue often extends into the pulmonary veins. It is in this tissue that the rapid atrial tachycardias originate. In this procedure, complete electrical isolation of the atrial tissue insertions into the pulmonary veins is accomplished. There are currently two different techniques: 1) isolating each pulmonary vein separately, and 2) isolating them in blocks of two or even four. Each one requires documentation of electrical silence of the pulmonary veins, with either a lasso or basket catheter. In either technique, cure rates are higher than focal ablation of triggers, and isolation of the pulmonary veins has become the standard procedure for the ablation of atrial fibrillation. Whether block isolation or single isolation is most likely to be curative is not yet defined. Complications of these procedures include stroke and pulmonary vein stenosis. Future treatment advances in atrial fibrillation are likely to occur with the development of new hardware and techniques. Devices that enable more complete and safer isolation of the pulmonary veins are likely to be seen. Patient selection for these procedures will continue to be defined. In the past, most individuals referred for catheter ablation had lone atrial fibrillation; however, patients with valvular and other cardiac conditions are increasingly being brought to the electrophysiology laboratory. In conclusion, radiofrequency ablation has revolutionized the treatment of atrial fibrillation. Future developments in the ablation technique and definition of the patient population will continue. Yet, anticoagulation must not be forgotten, and anti-arrhythmic agents will still be utilized for many patients.