Objective: In dialysis patients, volume overhydration is common and is related to increased risk of cardiovascular morbidity and mortality. However, it remains unclear whether volume overload imposes those detrimental effects through endothelial dysfunction. Methods: In this cross-sectional study, 81 stable patients on continuous ambulatory peritoneal dialysis in a single center were recruited. Volume status was evaluated by extracellular water, assessed by bioimpedance analysis, and normalized to individual height ( nECW). Endothelial function was estimated by endothelial-dependent flow- mediated dilatation ( FMD) of the brachial artery and expressed as percentage change relative to baseline diameter. Results: There were 37 male and 44 female patients ( mean age 61 +/- 12 years, dialysis vintage 20 +/- 23 months). FMD in female patients was 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 product ( beta = 0.422, p < 0.001), nECW ( beta = -0.343, p < 0.01), and dialysis vintage (beta = -0.237, p < 0.05) were independent determinants of FMD ( adjusted R-2 = 0.327 for this model). Conclusion: There was independent correlation between index of volume status and FMD, and higher nECW was related to worse endothelial function. The results of this study may help us understand the underlying mechanism of volume overhydration leading to increased cardiovascular morbidity and mortality in dialysis patients.