AbstractBackground: Inflammation plays the key role in pathogenesis of coronary artery disease. Various studies in literature has shown relation between various hematological parameters and coronary artery disease. But relation between these hematological parameters and severity of coronary artery disease is less studied. Aim: To know relation between various hematological parameters and severity of coronary artery disease. Method: We enrolled a total of 101 patients with ST elevation myocardial infarction who underwent coronary angiography. In control group, 31 patients were taken with normal coronary angiogram. White blood count, Neutrophil %, Lymphocyte %, Neutrophil/lymphocyte ratio, Platelet count, Red cell distribution width, Mean platelet volume, Platelet distribution width, Large platelet concentration ratio, HBA1c and Troponin I were taken. Coronary artery disease severity is assessed by SYNTAX score. Results: Age distribution was similar between cases and control (p = 0.921). Males were predominant among both cases and control. Patients with coronary artery disease had higher white blood cell count, neutrophil count, neutrophil/lymphocytic ratio, red cell distribution width, mean platelet volume, platelet distribution width, large platelet concentration ratio. A very weak correlation was found between syntax score and white blood cell count, neutrophil-lymphocyte ratio, red cell distribution width, mean platelet volume, platelet distribution width and large platelet concentration ratio which is statistically insignificant too. But a significant correlation was found between SYNTAX score and glycosylated hemoglobin and troponin I levels in acute coronary syndrome. Conclusion: Hematological parameters does not have good correlation with syntax score except Troponin I and HBA1c, for predicting coronary artery disease severity.