Atrial fibrillation is the most common cardiac arrhythmia in adults. Paroxysmal atrial fibrillation terminates spontaneously, whereas the persistent form terminates only after medical or electrical cardioversion. Permanent atrial fibrillation cannot be cardioverted. Restoration of sinus rhythm can be achieved by antiarrhythmic drugs or electrical cardioversion, both performed under continuous electrocardiographic monitoring. If atrial fibrillation has lasted longer than 48 hours or the precise time of onset cannot be determined, there are two alternative approaches: systemic anticoagulation to achieve an international normalised ratio (INR) of 2.0 to 3.0 for at least three weeks, followed by cardioversion; or cardioversion guided by transesophageal echocadiography indicating the absence of thrombus. Several drugs have been shown to be effective for the maintenance of sinus rhythm. Anticoagulant therapy is mandatory for a minimum of three weeks after cardioversion. In case of drug refractory, highly symptomatic atrial fibrillation the indication for radiofrequency catheter ablation should be discussed, although the value of this new method is still under evaluation.