Background: Time to reperfusion and acute kidney injury (AKI) are powerful prognostic markers in ST segment elevation myocardial infarction (STEMI) patients undergoing percutaneous coronary intervention (PCI), however no information to date is present regarding the association between time to reperfusion and AKI. We evaluated whether time to reperfusion predicts the risk of AKI among STEMI patients undergoing primary PCI.Methods: Medical records of 417 patients admitted to our department between January 2006 and July 2013, for STEMI and treated with primary PCI were reviewed. Patients' were stratified by time to reperfusion tertiles and their records were assessed for the occurrence of AKI following PCI.Results: Mean age was 61 ± 13 years and 346 (83%) were male. The cut-off points for the time to reperfusion tertiles were <120 minutes, 120-300 minutes, and >300 minutes. Patients having longer time to reperfusion had more AKI complicating the course of STEMI (3% vs. 11% vs. 13%, p = 0.007) and had significantly higher serum creatinine change throughout hospitalization (0.13 mg/ dl vs. 0.18 mg/dl vs.0.21 mg/dl p < 0.001). In a multivariable logistic regression model time to reperfusion emerged as an independent predictor of AKI (OR 1.001, 95% CI 1.000-1.001, p = 0.04).Conclusion: Longer time to reperfusion in is an independent risk factor for the development of AKI in STEMI patients undergoing primary PCI.