Background— Endocardial voltage mapping (EVM) identifies low-voltage right ventricular (RV) areas, which may represent the electroanatomic scar substrate of life-threatening tachyarrhythmias. We prospectively assessed the prognostic value of EVM in a consecutive series of patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D). Methods and Results— We studied 69 consecutive ARVC/D patients (47 males; median age 35 years [28–45]) who underwent electrophysiological study and both bipolar and unipolar EVM. The extent of confluent bipolar (<1.5 mV) and unipolar (<6.0 mV) low-voltage electrograms was estimated using the CARTO-incorporated area calculation software. Fifty-three patients (77%) showed ≥1 RV electroanatomic scars with an estimated burden of bipolar versus unipolar low-voltage areas of 24.8% (7.2–31.5) and 64.8% (39.8–95.3), respectively ( P =0.009). In the remaining patients with normal bipolar EVM (n=16; 23%), the use of unipolar EVM unmasked ≥1 region of low-voltage electrogram affecting 26.2% (11.6–38.2) of RV wall. During a median follow-up of 41 (28–56) months, 19 (27.5%) patients experienced arrhythmic events, such as sudden death (n=1), appropriate implantable cardioverter defibrillator interventions (n=7), or sustained ventricular tachycardia (n=11). Univariate predictors of arrhythmic outcome included previous cardiac arrest or syncope (hazard ratio=3.4; 95% confidence interval, 1.4–8.8; P =0.03) and extent of bipolar low-voltage areas (hazard ratio=1.7 per 5%; 95% confidence interval, 1.5–2; P <0.001), whereas the only independent predictor was the bipolar low-voltage electrogram burden (hazard ratio=1.6 per 5%; 95% confidence interval, 1.2–1.9; P <0.001). Patients with normal bipolar EVM had an uneventful clinical course. Conclusions— The extent of bipolar RV endocardial low-voltage area was a powerful predictor of arrhythmic outcome in ARVC/D, independently of history and RV dilatation/dysfunction. A normal bipolar EVM characterized a low-risk subgroup of ARVC/D patients.