RDW is a marker of the variability in erythrocyte Vol.ume and is a routinely available component of the complete blood count. Clinical usage of RDW has usually been restricted to differential diagnosis of anemia. However, elevated RDW levels are associated with poor prognoses in acute myocardial infarctions (MI) heart failures stable angina in patients undergoing PCI and general population even in the adjustment for multiple potential confounders, including anemia.The aim of this study is to evaluate the predictive value of red cell distribution width (RDW) on the electrocardiographic and angiographic no-reflow phenomenon in patients undergoing primary percutaneous coronary intervention (PCI).A total of 72 patients were included in this prospective cohort study. The study population was divided into two groups • Group (I): 54 patients with post-procedure ST-T resolution ≥ 50%. • Group (II): 18 patients with post-procedure ST-T resolution < 50%. Results of the current study showed that there was significant difference between the 2 groups regarding RDW (P= 0.003), LV systolic function (P= 0.040), TIMI flow after PPCI (P= 0.006) and MBG post PCI (P= 0.002). Also there was significant difference regarding in-hospital MACE (P= 0.023). Cut-off value for RDW as a predictor of outcome was ≥ 14.3 % with accuracy of 68% i.e. the higher the RDW the worse outcome result should be predicted out of PCI results. So, more focused care should be delivered to patients presented with STEMI and high RDW value.