BACKGROUND Acute kidney injury (AKI) after coronary angiography (CAG) and primary percutaneous coronary intervention (PPCI) is frequently observed, and often interpreted as contrast induced-AKI. This study aimed to investigate the incidence, predictors and outcomes of AKI in acute ST-segment elevation myocardial infarction (STEMI) patients undergoing emergent CAG/ PPCI using the control group of STEMI patients who were not exposed to contrast agents within the first 72 h. METHODS We performed a retrospective analysis of 1670 STEMI patients. Of them, 673 patients underwent emergent CAG/PPCI, and 997 patients treated with thrombolysis or no reperfusion therapy who were not exposed to contrast material during the first 72 h. AKI was defined as an increase of serum creatinine = 44.2 mmol/L or = 25% from baseline within 72 h. Patents were then followed up for the occurrence of all-cause mortality for 40 months (interquartile range: 24-55 months). RESULTS After propensity score matching, 505 pairs of patients were matched. Overall, the incidence of AKI was 27.4%, and AKI rates were not significantly different in patients with and without emergent CAG/PPCI procedure (27.5% vs. 27.3%, P = 0.944). Multivariate logistic regression analysis identified that the independent predictors of AKI were female, elevated interleukin-6 level, decreased lymphocyte count, left ventricular ejection fraction < 50% and use of diuretics in patients with emergent CAG/PPCI. Patients with AKI than those without AKI experienced higher incidence of acute heart failure with Killip class III (9.4% vs. 3.3%, P = 0.005; 15.2% vs. 6.8%, P = 0.003, respectively) and mortality (5.8% vs. 1.4%, P = 0.014; 12.3% vs. 4.6%, P = 0.002, respectively) in patients with and without emergent CAG/PPCI. Multivariate Cox regression analysis confirmed that AKI was independently associated with long-term mortality rate at 40 months follow-up in patients with and without emergent CAG/PPCI (HR = 1.867, 95% CI: 1.086-3.210, P = 0.024; HR = 1.700, 95% CI: 1.219-2.370, P = 0.002, respectively). CONCLUSIONS Approximately 27.0% of STEMI patients experience AKI, which is strongly associated with an increased shortand long-term mortality regardless of emergent CAG/PPCI procedure. The development of AKI is mainly related to female gender, inflammation reaction, heart failure and use of diuretics in STEMI patients undergoing emergent CAG/PPCI.