We sought to evaluate the prognostic significance of ST-segment elevation (STE) in lead aVR in unselected patients with non-STE acute coronary syndrome (NSTE-ACS). We enrolled 1,042 consecutive patients with NSTE-ACS. Patients were divided into 5 groups according to the following electrocardiographic (ECG) patterns on admission: (1) normal electrocardiogram or no significant ST-T changes, (2) inverted T waves, (3) isolated ST deviation (ST depression [STD] without STE in lead aVR or transient STE), (4) STD plus STE in lead aVR, and (5) ECG confounders (pacing, right or left bundle branch block). The main angiographic end point was left main coronary artery (LM) disease as the culprit artery. Clinical end points were in-hospital and 1-year cardiovascular death defined as the composite of cardiac death, fatal stroke, and fatal bleeding. Prevalence of STD plus STE in lead aVR was 13.4%. Rates of culprit LM disease and in-hospital cardiovascular death were 8.1% and 3.8%, respectively. On multivariable analysis, patients with STD plus STE in lead aVR (group 4) showed an increased risk of culprit LM disease (odds ratio 4.72, 95% confidence interval [CI] 2.31 to 9.64, p <0.001) and in-hospital cardiovascular mortality (odds ratio 5.58, 95% CI 2.35 to 13.24, p <0.001) compared to patients without any ST deviation (pooled groups 1, 2, and 5), whereas patients with isolated ST deviation (group 3) did not. At 1-year follow-up 127 patients (12.2%) died from cardiovascular causes. On multivariable analysis, STD plus STE in lead aVR was a stronger independent predictor of cardiovascular death (hazard ratio 2.29, 95% CI 1.44 to 3.64, p <0.001) than isolated ST deviation (hazard ratio 1.52, 95% CI 0.98 to 2.36, p = 0.06). In conclusion, STD plus STE in lead aVR is associated with high-risk coronary lesions and predicts in-hospital and 1-year cardiovascular deaths in patients with NSTE-ACS. Therefore, this promptly available ECG pattern could be useful to improve risk stratification and management of patients with NSTE-ACS.