Usefulness of 12-lead ECG for predicting an epicardial origin for ventricular tachycardia (VT) arising from the right ventricle (RV) has not been assessed. An epicardial approach is sometimes warranted to eliminate RV VT. The purpose of this study was investigate the hypothesis that specific ECG features identify an epicardial origin for RV VT. To mimic an endocardial or epicardial origin, we paced representative sites in 13 patients undergoing RV endocardial/epicardial mapping (134/180 pace map sites). QRS duration from epicardial vs endocardial sites was not different (183 +/- 27 ms vs 185 +/- 28 ms, P = .3). Reported cut-off values for identifying epicardial left ventricular origin, pseudo-delta wave (> or =34 ms), intrinsicoid deflection time (> or =85 ms), and RS complex (> or =121 ms) did not apply to the RV. A Q wave in lead II, III, or aVF was more likely noted from inferior epicardial vs endocardial sites (53/73 vs 16/43, P <.01). A Q wave in lead I was more frequently present from epicardial vs endocardial anterior RV sites (30/82 vs 5/52, P <.001). QS in lead V(2) was noted from anatomically matched epicardial anterior RV sites (22/33 vs 13/33, P <.05). In the RV outflow tract, no ECG feature distinguishing epicardial/endocardial origin reached statistical significance. A Q wave or QS in leads that best reflect local activation suggest an epicardial origin for RV depolarization and may help in identifying a probable epicardial site of origin for RV VT. QRS duration and reported criteria for epicardial origin of VT in the left ventricle do not identify a probable epicardial origin in the RV.