PURPOSE: The aim of this study was to confirm the expression of high mobility group box 1 (HMGB1) in patients with epithelial ovarian cancer (EOC) and to evaluate the prognostic significance of HMGB1. METHODS: A total of 74 patients with EOC comprised our cohort. Retrospectively collected tissue microarray from EOC patients treated with debulking surgery followed by taxane and platinum chemotherapy were analyzed for evaluation of the prognostic significance of HMGB1. Expression of HMGB1 was assessed by immunohistochemistry. RESULTS: The positive staining was detected in 80% of EOC patients and the rate of high HMGB1 expression was 42%. In advanced stage, patients with high HMGB1 expression showed a poorer prognosis than low HMGB1 expression group [median progression-free survival (PFS), 10.8 vs. 21.7 months, P = 0.005]. High HMGB1 expression was an independent predictor for PFS (P = 0.024). CONCLUSIONS: HMGB1 expression is expected as a promising biomarker for EOC and further studies are needed to assess potential roles in EOC.