Objective High mobility group box protein-1 (HMGB1) is a newly recognized molecule behaving as an important extracellular mediator in systemic inflammation. Systemic inflammation results in endothelial cell activation and vascular injury. In the present study, we determined serum HMGB1 level in patients on maintenance hemodialysis (MHD), and assessed the HMGB1 level in association with microinflammation biomarkers and endothelial dysfunction. Methods During the period of March 2009 through April 2009, 89 patients (46 male, 43 female, mean age 56.54±10.72 years) with end stage renal dysfunction on MHD (for 65.2±54.7 months) as well as 31 healthy volunteers were investigated. Their disease status was stable, and they had no evidence of vascular disease and/or active infection. Serum levels of HMGB1, TNF-α, sVCAM1 and E-selectin were measured by ELISA. Results Serum HMGB1 in patients was 5.10±1.93μg/L, significantly higher than that in healthy volunteers (2.20±0.31μg/L, n=31). Serum HMGB1 positively correlated with TNF-α (r=0.711, P＜0.01), IL-6 (r=0.804, P＜0.01), soluble vascular cell adhesion molecule 1 (sVCAM1) (r=0.454, P＜0.01), and E-selectin (r=0.601, P＜0.01), but negatively correlated with Hb (r=-0.26, P=0.013) and Alb (r=-0.372, P＜0.01). Serum HMGB1 did not correlate with total cholesterol, triglyceride and blood glucose. Conclusions Higher serum HMGB1 was frequently found in MHD patients, probably reflecting the vascular endothelial injury in these patients. Therefore, serum HMGB1 may be used clinically as a microinflammation biomarker in MHD patients.