Apart from endocrine and reproductive disturbances, polycystic ovary syndrome (PCOS) clusters several cardiovascular risk factors, mainly insulin resistance, obesity and dyslipidemia. In addition, androgen excess significantly contributes to enhanced vascular risk. Several mediators of endothelial dysfunction have been characterized lately in patients with PCOS, emerging as independent predictors of vascular abnormalities and potentially useful biomarkers of endothelial impairment in PCOS.