PCOS (polycystic ovary syndrome) is associated with reproductive abnormalities, IR (insulin resistance) and elevated risk factors for CVD (cardiovascular disease) and Type 2 diabetes, including endothelial dysfunction. The present study aimed to assess a range of circulating markers of endothelial function in overweight women with and without PCOS. Overweight and obese age- and BMI (body mass index)-matched women with (n=80) and without (n=27) PCOS were assessed in a cross-sectional study. End-point measures were HOMA (homoeostasis model assessment)-IR, androgens, lipids, inflammatory markers [hsCRP (high-sensitivity C-reactive protein)] and endothelial function [FMD (flow-mediated dilation), ADMA (asymmetric dimethylarginine), PAI-1 (plasminogen activator inhibitor-1) and vWF (von Willebrand factor)]. Women with PCOS had elevated HOMA-IR (4.1+/-3.4 compared with 1.9+/-1.4), free androgen index (9.3+/-5.6 compared with 4.6+/-3.8), total cholesterol (5.2+/-1.0 compared with 4.7+/-0.9 mmol/l) and triacylglycerols (triglycerides; 1.4+/-0.7 compared with 0.9+/-0.3 mmol/l) (P<0.05 for all), but similar hsCRP compared with women without PCOS. With regard to endothelial function, women with PCOS had elevated ADMA (1.0+/-0.4 compared 0.3+/-0.1 mumol/l, P<0.001) and PAI-1 (5.6+/-1.8 compared with 4.6+/-1.1 units/ml, P=0.006), a trend towards worsened FMD (11.8+/-5.0 compared with 13.5+/-4.0%, P=0.075) and no difference in vWF compared with controls. For all subjects, ADMA (P=0.002) and PAI-1 (P<0.001) were increased with higher tertiles of HOMA-IR. Women with PCOS are hyperandrogenic, dyslipidaemic and have IR, and have risk factors for CVD and diabetes including increased circulating markers of endothelial function (ADMA and PAI-1) and a trend towards worse FMD as a global marker of endothelial function. In PCOS, deterioration in endothelial function is related to IR, hyperandrogenism and other factors.