Objective: We aimed to assess relationship between the severity of coronary atherosclerosis assessed by SYNTAX score (SS) and neutrophil to lymphocyte ratio (NLR) in patients with ST elevation myocardial infarction (STEMI. Methods: After accounting for exclusion criteria, a total of 291 patient with STEMI in whom primary percutaneous coronary intervention was performed were retrospectively included (216 male, 75 female; mean age 61.6+14.0 years). Total and differential leukocyte counts and other biochemical markers were measured at admission. Patients were categorized into tertiles on the basis of SS. Monitoring for major adverse cardiac events (MACEs) was performed during the in hospital follow-up period.Results: The SS high group leukocyte (p=0.009), neutrophil (p=0.008), NLR (p=0.048), peak troponin (p<0.001), peak CK-MB (p=0.001) lactate dehydrogenase (p=0.005), aspartate aminotransferase (p=0.004) values were significantly higher compared with SSlow and SSmid groups. SS was increased, left ventricular ejection fraction was decrease (p<0.001) and left ventricular systolic diameter was increased (p=0.007). The in-hospital death rate and MACEs were greater in the high SS group than in the other groups (p<0.001 both of). Conclusion: We found that high NLR was significantly and correlated increased with SS. In addition, high SS were significantly associated with increased in-hospital MACE and in-hospital death. Further prospective studies assessing the predictive role of both SS and NLR in conjunction for risk stratification might improve risk prediction in patients with STEMI.