Objective:In this study, we aimed to explore the association between platelet-to-lymphocyte ratio (PLR) and the severity of atherosclerosis in coronary artery disease (CAD).Methods:Clinical and laboratory data of 388 patients who underwent coronary angiography were evaluated retrospectively. Gensini score, which indicates the severity of atherosclerosis, was calculated for all of the patients. Patients with CAD were categorized as mild and severe atherosclerosis, according to their Gensini score. Eighty patients with normal coronary arteries formed the control group. Mean PLR values of the three study groups were compared. Also, PLR value was tested for whether it showed a positive correlation with Gensini score.Results:The mean PLR of the severe atherosclerosis group was significantly higher than that of the mild atherosclerosis and controls groups (p<0.001). Also, PLR was positively correlated with Gensini score in CAD patients. A cut-off value of 111 for PLR predicted severe atherosclerosis with 61% sensitivity and 59% specificity. Pre-procedural PLR level was found to be independently associated with Gensini score, together with WBC, age, and low HDL level, in the multivariate analysis.Conclusion:Our study suggests that high PLR appears to be additive to conventional risk factors and commonly used biomarkers in predicting severe atherosclerosis.