Four neonates with Wolff-Parkinson-White syndrome developed supraventricular tachycardia and received flecainide orally after reduction of the arrhythmia. The initial doses were 5 mg/kg/day. They are increased according to clinical response and flecainide concentrations, with 5 and 10 mg/kg/24 h respectively, were in the therapeutic range of 200 to 1000 micrograms/l. Flecainide was effective and well tolerated in the 4 cases. Therefore, this drug may be an alternative to digoxine to prevent supraventricular tachycardias in the neonatal period.