The prognostic value of integrated R-wave voltages of precordial leads (V(1)-V(6)) in patients with acute anterior wall ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI) was investigated. Between July 2006 and October 2009, 292 patients with anterior wall STEMI with presentation < 12 hours underwent primary PCI. Thirty-four patients with electrocardiographic presentation of either complete right bundle branch block (BBB) or complete left BBB were categorized into group A, while the remaining 258 patients without BBB served as group B that was further subdivided into those with lower R-wave voltage (summation of V(1)-V(6) ≤ 1.7 mV) (group 1) and higher voltage (> 1.7 mV) (group 2) according to the ROC curve (sensitivity = 66.3%, specificity = 66%, P < 0.0001).While the procedural success rate was similar between groups A and B and groups 1 and 2, 30-day mortality was higher in group A than B (P ≤ 0.0001). Additionally, left ventricular ejection fraction (LVEF) was lower, whereas peak level of creatine phosphokinase (CPK), incidence of advanced congestive heart failure, and 30-day mortality were higher in group 1 than 2 (P < 0.01). Multivariate analysis revealed that lower R-wave voltage, multivessel disease, leukocyte count, peak CPK, and creatinine level were predictive of 30-day unfavorable clinical outcomes (all P < 0.01). R-wave voltage in precordial leads was a significant independent predictor of 30-day prognostic outcome in patients with anterior wall STEMI undergoing primary PCI.