['The aim of this study was to evaluate osteopontin (OPN) mRNA expression in eutopic endometrium and plasma OPN levels in patients with endometriosis.', 'A total of 79 patients with histologically confirmed endometriosis and 43 patients without endometriosis participated in this study. OPN mRNA expression in endometrial tissues was measured by real-time quantitative polymerase chain reaction (PCR) and plasma concentrations of OPN were quantified using a specific commercial sandwich enzyme-linked immunosorbent assays (ELISA).', 'Osteopontin mRNA expression in endometrial tissue was significantly higher in women with endometriosis than in controls (P = 0.010). The mean plasma levels of OPN (mean +/- S.E.M.) in patients with endometriosis and controls were 407.31 +/- 37.80 ng/mL and 165.84 +/- 19.29 ng/mL, respectively (P < 0.001). Receiver operating characteristic (ROC) analysis for plasma OPN revealed an area under the curve (AUC) of 0.894, with a sensitivity of 93.0%, specificity of 72.4%, positive likelihood ratio of 3.37, and negative likelihood ratio of 0.1 using a cut-off value of 167.68 ng/mL.'] Are endometrial osteopontin mRNA expression and plasma osteopontin levels increased in patients with endometriosis?