We report a case about a 27-year-old healthy young male who developed syncope during exercise, which was subsequently identified to be attributable to non-sustained polymorphic ventricular tachycardia (VT). Occurrence of polymorphic VT was neither related to a prolonged QT interval nor a fixed short coupling interval. Standard examinations including echocardiography, coronary angiography, isoproterenol infusion study, and cardiac MRI showed no structural heart disease. On the electrophysiology study, activation mapping revealed that a discrete potential preceded the premature ventricular complex (PVC) triggered polymorphic VT, which was recorded just above the pulmonary valve. After radiofrequency ablation at this area, PVC and polymorphic VT disappeared and did not recur after a 2 month follow up.