Aim To investigate whether volume overload poses its detrimental effect on cardiovascular mortality through endothelial dysfunction. Methods In this cross-sectional study,81 stable patients on continuous ambulatory peritoneal dialysis(CAPD) in a single center were recruited.Volume status was evaluated with extracellular water normalized by individual height(NECW),which was assessed by bioimpedance analysis.Endothelial function was estimated by endothelial-dependent flow-mediated dilatation(FMD) of the brachial artery,which was expressed as the percentage change relative to the baseline diameter. Results There were 37 male and 44 female patients.Their mean age and dialysis duration were 61±12 years and 20±23 months,respectively.The FMD in female patients were significantly higher than that in male patients(9.17%±6.23% vs 6.31%±5.01%,P<0.05).FMD was negatively correlated with weight(r=-0.308,P<0.01),body mass index(r=-0.242,P<0.05),systolic blood pressure(r=-0.228,P<0.05),ECW(r=-0.404,P<0.001) and NECW(r=-0.418,P<0.001).No correlation was found between FMD and other variables.In multiple stepwise regression analysis,calcium x phosphate(Ca x P) product(β=0.422,P<0.001),NECW(β=-0.343,P<0.01) and dialysis duration(β=-0.237,P<0.05) were independent determinants of FMD(adjusted R2=0.327 for this model). Conclusion Higher NECW was related to worse endothelial function.The results in this study may help us to understand the underlying mechanism of volume overload leading to increased cardiovascular morbidity and mortality in dialysis patients.