38-year-old male who had paroxysmal atrial fibrillation which was electrocardiograpm-cally very mimic to ventricular tachycardia was studied. This case was also confirmed as having ventricular septal defect (Roger's disease) by means of chest roentgenograms, right heart catheterization and phonocardiogram. Some considerations on the causes, etiology, complications and therapy of this type of arrhythmia were made.