Objective: In this study, we randomly compared single oral doses of flecainide, amiodarone and propafenone versus placebo for the conversion of recent atrial fibrillation (AF) (within 48 hours). Methods: This is a randomized prospective, placebo-controlled single-blind study that included 160 consecutive patients with recent AF who were randomly assigned to single oral doses of flecainide (3 mg/kg of weight, n=40), amiodarone (30 mg/kg weight, n=40), propafenone (8.5 mg/kg of weight, n=40) or placebo (n=40). The primary end-point was conversion rate at 24 hours after the drug intake. The association between antiarrhythmic use and conversion rate was tested with multiple logistic regressions. Results: The primary end-point was achieved in 87.5% of patients with flecainide, 85% of patients with amiodarone, 85% of patients with propafenone and 17.5% of patients with placebo (p<0.001 compared with placebo for all 3 drugs). Conversion rate within 3 hours after drug intake was greater with propafenone (57.5%) or flecainide (45%) compared with amiodarone (0%) or placebo (10%). Between 6 and 24 hours, significantly more patients were converted to sinus rhythm with amiodarone than with flecainide or propafenone. The use of antiarrhythmic drugs was a significant predictor of conversion to sinus rhythm compared to placebo (adjusted OR=19.53, 95% CI 3.14-121.55, p<0.001). No serious side effect occurred. Conclusion: In patients with recent-onset AF, oral flecainide, amiodarone or propafenone are superior to placebo in restoring sinus rhythm within the 24-hour period following the drug intake.