The present study is designed to test whether catheter based radiofrequency ablation is superior to optimized antiarrhythmic medical therapy in suppressing long-term relapse of symptomatic and/or asymptomatic atrial fibrillation in patients who are not already in chronic pharmaceutical antiarrhythmic therapy. Secondary end points are: mortality, thromboembolic events, hospitalization due to disturbance in heart rhythm, proarrhythmic events, procedure/treatment related side effects, health economics and quality of life. Comparison will be made after two years follow-up and a register follow-up will take place after additional 3 years (a total of at least five years of follow-up).