['White blood cell count is an independent predictor of cardiovascular events and mortality. Neutrophil/lymphocyte ratio (NLR) is a biomarker that can single out individuals at risk for vascular events.', 'To evaluate whether NLR adds additional information beyond that provided by conventional risk factors and biomarkers for coronary artery disease (CAD) severity and adverse outcome, in a large cohort of consecutive patients referred for coronary angiography.', 'NLR was computed from the absolute values of neutrophils and lymphocytes from the complete blood count of 3005 consecutive patients undergoing coronary angiography for various indications. CAD severity was determined by an interventional cardiologist unaware of the study aims. The association between NLR and CAD severity was assessed by logistic regression and the association between NLR and 3-years outcome were analyzed using Cox regression models, adjusting for potential clinical, metabolic, and inflammatory confounders.', 'The cohort was divided into 3 groups according to the NLR value (<2, 2-3, and >3). NLR was independently associated with CAD severity and it contributed significantly to the regression models. Patients with NLR >3 had more advanced obstructive CAD (OR = 2.45, CI 95% 1.76-3.42, p < 0.001) and worse prognosis, with a higher rate of major CVD events during up to 3 years of follow-up (HR = 1.55, CI 95% 1.09-2.2, p = 0.01).'] Is neutrophil/lymphocyte ratio related to the severity of coronary artery disease and clinical outcome in patients undergoing angiography?