Objective:The aim of the present study was to examine a possible association between inflammation, as indicated by High-sensitivity C-reactive protein (HsCRP) and neutrophil/lymphocyte ratio (NLR), and the complexity and severity of coronary artery disease assessed using syntax severity score (SSS) in patients with acute coronary syndrome (ACS). Methods:Patients with symptoms suggestive of ACS who were admitted within 6 h of onset and who underwent coronary angiography were enrolled in the study. According to NLR, we divided patients into two groups: group 1 (NLR≤2.7) and group 2 (NLR>2.7). According to SSS, patients were divided into two groups: group 1 including low scores and group 2 including intermediate and high scores. Statistical analysis was performed using chi-square test and Mann-Whitney U test.Results: A total of 87 patients (65 males and 22 females) with acute myocardial infarction (AMI; 57 ST-se AMI and 30 non-STse AMI) were included in this study. Patients were classified into low (NLR≤2.7, n=63) and high (NLR>2.7, n=24) NLR groups. Univariate a>nalysis demonstrated that SSS was significantly higher in high NLR group than in low NLR group (23.6±12.7 versus 13.9±8.7, p<0.001). Similar to NLR, significant correlation was revealed among HsCRP, troponin levels, and SSS that indicated their predictive value in the severity of AMI. Conclusion:In present study, we showed NLR to be an independent predictor of hemodynamically significant coronary artery stenosis as measured using SSS.