Conversion of atrial flutter and atrial fibrillation (AF) can be achieved by either pharmacologic or direct-current (DC) electrical cardioversion. DC electrical cardioversion is more effective and restores sinus rhythm instantaneously; however, general anesthesia is necessary, which can cause severe complications. On the other hand, pharmacologic cardioversion is less effective. First, time to conversion is unpredictable and may be relatively long, especially with oral drug therapy. Also, the rate of conversion is lower and depends on duration of AF. In addition, safety is an important issue. Adverse drug reactions include bradycardia, paradoxical tachycardia due to enhanced atrioventricular conduction, ventricular proarrhythmia, and acute heart failure. In paroxysmal AF, drug therapy is usually aimed at an acute conversion. Class IA and IC drugs are more efficacious than the class III drugs sotalol, amiodarone, and ibutilide. By contrast, class III drugs are more effective for the conversion of atrial flutter. Acute conversion out-of-hospital (“pill in the pocket approach”) should be done only if the drug used appeared effective and safe after a few in-hospital trials. In persistent AF, DC conversion is preferred because drugs are particularly ineffective if the arrhythmia has lasted >24–48 hours. The latter probably relates to electrical and anatomical remodeling of the atria during ongoing atrial fibrillation and flutter. Nevertheless, a wait-and-see approach using, for example, oral amiodarone may be adopted with late DC conversion if the drug fails to convert persistent AF. However, the consequences of remodeling seem to dictate an early conversion. In this respect, echocardiography-guided DC cardioversion may become increasingly important in AF. It will prevent treatment resistance and potentially reduces embolic complications. In a hybrid approach, antiarrhythmic drugs may be used to enhance DC conversion and prevent (sub)acute recurrences of AF. However, it may increase the defibrillation threshold, especially if class IC drugs are used. New treatment options such as automatic defibrillation (implantable atrioverter) are still investigational.