Aim: We aimed to investigate whether baseline monocyte to high-density lipoprotein cholesterol ratio (MHR), an easily available inflammatory and oxidative stress marker, is associated with SYNTAX score. Patients & methods: In this cross-sectional study, n = 1229 consecutive patients with coronary artery disease were classified into two groups, low SYNTAX score (<= 22) and high SYNTAX score (>= 23). Results: MHRs were significantly higher in patients with high SYNTAX score (p < 0.05). In multivariate regression analysis, MHR remained as independent predictor of high SYNTAX score together with C-reactive protein (CRP), hypertension and diabetes mellitus. In correlation analysis, MHR showed significant positive correlations with SYNTAX score (r = 0.371, p < 0.001) and CRP level (r = 0.336, p < 0.001). Conclusion: This study suggests MHR is independently associated with burden of coronary atherosclerosis.