Background Drug-refractory monomorphic ventricular tachyarrhythmia (MVT) in patients with structurally normal hearts is an excellent candidate for radiofreuquency catheter ablation (RFCA). However, clinical outcome of RFCA targeted to the unusual foci has not yet been reported. Methods and Results We performed RFCA on 143 patients (56.0% male, 42.5짹13.3 years old) who had either idiopathic ventricular tachycardia (VT; n=81) or drugs (>2) refractory frequent premature ventricular contractions (PVCs; n=62). We analyzed the clinical outcomes and electrocardiographic (ECG) characteristics of ventricular arrhythmias, excluding the arrhythmias originating from either the outflow tract (OT) VT or idiopathic left ventricular (LV) VT (ILVT). Results: 1. MVTs originated from right ventricular (RV) OT (49.0%), LVOT or aortic cusp (16.1%), ILVT (9.1%), LV mid anterolateral wall (LV-MAL; 6.3%), Epicardial interventricular groove (EIV; 6.3%), RV inflow tract (RVIT; 5.6%), mitral annulus (MA; 2.1%), pulmonary artery (PA; 2.1%), RV midseptum (RV-MS; 2.1%), or tricuspid annulus (TA; 1.4%). Eleven (7.1%) patients had multiple foci. 2. ECG morphology of MVT of LV-MAL origin MVT showed right axis deviation (100% vs. 25%, p<0.001) and inferior axis (88.9% vs. 0%, p<0.001) as compared with those of ILVT. EIV-origin MVT showed longer intrinsicoid deflection time (108.9짹22.6 ms vs. 61.8짹23.0 ms, p<0.001) than that of LVOT-origin MVT. RVIT origin had tall lead I (5.42짹1.81 mV vs. 1.13짹1.36 mV, p<0.001) compared with RVOT, and the target site was very close to His bundle. 3. The post-RFCA PVC recurrences were significantly greater in patients with MVT originated from LV-MAL (22.2%), EIV (63.5%), and RVIT (42.9%) than those in patients with MVT from other origins (6.9%) during 21.7짹12.3 months of follow up. Conclusion MVTs originating from LV-MAL, EIV, or RVIT had characteristic ECG QRS morphologies, and they showed a higher recurrence rate after RFCA. Better mapping and ablation technology are warranted for caring these unusual foci of MVT.