Atrial fibrillation is the most common heart arrhythmia afflicting approximately 1% of the Danish population. Medical antiarrhythmic treatment is only moderately effective and has the risk of severe side effects. The present study is a prospective, randomized, multicentre study comparing medical antiarrhythmic drug strategy with catheter based radiofrequency strategy in patients with paroxysmal atrial fibrillation. The primary end point is atrial fibrillation burden (symptomatic and asymptomatic) judged by multiple 7-day Holter monitorings during 2 years follow-up. Three hundred patients considered candidates for antiarrhythmic drug treatment will be randomized. The study will be performed as a Scandinavian/German multicentre study.