Background: The clinical implication of high-degree (second and third) atrioventricular block (HAVB) complicating ST-segment elevation myocardial infarction (STEMI) was sparsely investigated in the era of primary percutaneous coronary intervention (PCI). We sought to address the incidence, predictor and prognosis of HAVB according to the location of infarct in STEMI patients treated with primary PCI. Methods: Total 16536 STEMI patients( Anterior infarction: n＝9354, Inferiorinfarction: n＝7692) who treated by primary PCI were enrolled from a multicenter registry. We compared the in-hospital mortality between patient with HAVB and those without HAVB in each anterior or inferior infarction. The multivariate analyses were performed to find out predictors of HAVB and to identify whether the HAVB is independently associated with in-hospital mortality. Results: The STEMI patients with HAVB showed higher in-hospital mortality than those without HAVB in both anterior (HR＝9.821, 95% CI:4.946-19.503, p ＜0.001) and inferior infarction (HR＝2.819, 95% CI: 2.076-3.827, p＜0.001). Although the old age and diabetes mellitus were predictors of HVAB in patient with inferior myocardial infarction (MI), these variable has no significant association with development of HAVB in patients with anterior MI. In multivariate analysis, the HAVB significantly increased in-hospital mortality in anterior MI (HR＝19.264, 95% CI: 5.804-63.936, p＜0.001). However, the HAVB in inferior infarction was not independently associated with increased in-hospital mortality (HR＝1.014, 95% CI: 0.547-1.985, p＝ 0.901). Conclusions: In era of primary PCI, the prognostic impact of HAVB was different according to the location of infarction. Especially, with the improvement of reperfusion strategy, the negative prognostic impact of HAVB in inferior STEMI was reduced.