Atrial fibrillation is the most commonly sustained cardiac arrhythmia and a common reason for mortality and morbidity. Atrial fibrillation causes disease for three reasons: i) the ventricular rate is often high, which leads to symptoms ranging from discomfort to life threatening heart failure; ii) the rhythm causes loss of atrioventricular synchrony, which reduces diastolic filling and may lead to heart failure; and iii) atrial contraction is lost leading to stagnant blood that again may lead to atrial thrombi and peripheral embolism. Thus, the treatment of atrial fibrillation is focused on the maintenance of sinus rhythm, rate control and prevention of embolism. For the maintenance of sinus rhythm, all drugs under current development are potassium channel blockers; the so-called class III anti-arrhythmic drugs. Those which have been further investigated appear to be valuable for maintenance of sinus rhythm but all carry a significant risk of pro-arrhythmia, in particular Torsade de Pointe ventricular tachycardia. Rate control has been a focus of treatment for many years and several very old drugs, including digoxin, are used for this. There is, to the author's knowledge, no current effort for evaluating new drugs for this indication. Prevention of embolism has for many years been obtained with vitamin K antagonists for which the clinical evidence is overwhelming. Previous attempts to replace vitamin K antagonists with aspirin have not been fruitful. A large number of newer anticoagulation regimes are in development, but to the author's knowledge only a single thrombin inhibitor is actively being developed for atrial fibrillation.