SummaryBactericidal/permeability-increasing protein (BPI), a major constituent of neutrophils that possesses anti-inflammatory properties, shows a structure similar to some proteins implicated in lipid metabolism. We evaluated circulating BPI as a biomarker of endothelial function and lipid metabolism. Circulating BPI concentrations (ELISA) and serum lipids were measured in 202 Caucasian non-smoking men. In a subgroup of 91 consecutive subjects brachial vascular reactivity (high resolution external ultrasound) was assessed. Plasma BPI concentrations were positively associated with total cholesterol (TC), LDL cholesterol (LDL-C) and HDL cholesterol (HDL-C) (r= 0.203, 0.204 and 0.18; all p<0.05, respectively). In a multiple linear regression analysis, BPI levels were independent contributors to the variance of HDL-C, total cholesterol and LDL-cholesterol after adjusting for age, body mass index and glucose tolerance status. Plasma BPI concentration correlated positively with endothelium-dependent vasodilatation (r=0.277; p<0.05) and HDL-C (r=0.36; p<0.05) in subjects with normal glucose tolerance. In conclusion, circulating BPI could constitute a biomarker of lipid metabolism in subjects with normal glucose tolerance and could help to identify those subjects with preserved endothelial function.