Background The incremental predictive value of red cell distribution width (RDW) on Korea Acute Myocardial Infarction Registry (KAMIR) score in patients with ST segment elevation myocardial infarction (STEMI) has not been assessed.This study was to investigate whether RDW had additional prognostic value on KAMIR score for predicting in-hospital death of STEMI patients.Methods Seven hundred and seven STEMI patients were included in this study.The predictive value was evaluated using the receiver operating characteristic (ROC).Multivariate logistic regression was used to determine risk predictors.Results Thirty four patients died while in hospital,who were older than those who survived,and had more proportion of Killip class ≥ 2 and no in -hospital PCI.Blood glucose,serum creatinine,white blood cell count,RDW and KAMIR score were significantly higher in the Death group,among whom systolic blood pressure,hemoglobin and LVEF were lower.ROC curve analysis showed RDW could predict in-hospital death,with the optimal cut-off values being 14.1％(AUC=0.707,95％CI,0.618-0.796,P＜0.001).When compared with the KAMIR score alone,the addition of RDW was associated with significant improvements in predicting in-hospital (AUC:0.865 vs.0.839,P=0.039).Conclusion RDW might provide additional information over the KAMIR score in STEMI patients.