The authors report the case of a patient with drug-resistant atrial fibrillation, who developed, for more than 2 hours, a well-tolerated attack of palpitations, after taking 500 mg of flecainide acetate. The Holter monitoring demonstrated atrial flutter with 1:1 AV conduction and a ventricular rate at 220 bpm. This atrial pro-arrhythmic effect is rare and the mechanism is discussed.