A 51-year-old man was admitted for evaluation of palpitation and syncope. Electrocardiography showed right bundle branch block with ST segment elevation. Intravenous administration of pilsicainide(50 mg) converted the saddle-back type into coved type ST elevation. Ventricular fibrillation was induced with double extrastimuli applied to the right ventricular outflow tract. His identical younger twin had neither symptoms nor abnormality by electrocardiography. Intravenous administration of pilsicainide(50 mg) induced no significant changes in the younger twin. Although SCN5A mutation is considered to be associated with Brugada syndrome, the present results suggest that the genetic factor is not the only factor responsible for the pathogenesis of Brugada syndrome.