Atrial fibrillation (Afib) is clinically the most common arrhythmia. Its main complications are recurrent embolic events and a variable deterioration of functional class. Atrial fibrillation induces changes in cellular ionic channels that self-perpetuate the arrhythmia. The pharmacologic treatment of Afib is directed toward correction of those changes and return to sinus rhythm. It is also intended to maintain adequate heart rates and prevent embolic events through anticoagulation or platelet antiagregation. There are presently several class IC or class III antiarrhythmics available for attempting a return to sinus rhythm. The success rates are irregular, the best achieved with flecainide or propafenone among patients without structural heart disease. Amiodarone is the best choice when there is such a problem. The combination possibilities are huge, so that each case must be individualized. The new class III antiarrhythmics are very effective, but have a relatively high rate of side effects including torsade de pointes. Anticoagulation should be the preferred treatment among the majority of patients, but each case should be individually evaluated. New therapies such as focal or linear catheter ablation techniques, atrial or biatrial programmed stimulation, and atrial cardioverter-defibrillator need longer follow-up and experience to be objectively evaluated, although there are reasons to be optimistic in the future, even if patients need antiarrhythmic support at present. Surgery has high morbi-mortality rates, so it is not the preferred approach.