Objective:To determine the role of Interleukine-8 in the pathogenesis of endometriosis(EM).Methods:36 patients with endometriosis were selected as study group.20 patients without endometriosis served as control group. IL-8 concentration in peritoneal fluid(PF) and serum of both groups were detected by ELISA.The correlation between IL-8 concentration and the severity of EM were performed.The differences of IL-8 mRNA expression in eutopic endometrium of patients between with and without endometriosis, and the differences among different endometriotic lesions were further studied by Northern Blot;Cultured endometrial stromal cells(CESC) were divided into groups. IL-8 and anti-IL-8 were used to treat these cells.Results:(1)The PF and serum from patients with EM contained significantly greater amounts of IL-8 than those in controls. A significant correlation between PF IL-8 content and the severity of disease was noted but there were no evidences of a relationship between concentrations of serum IL-8 and PF IL-8.(2) It was showed that the expression density of IL-8 mRNA of Eu were significantly higher than that of En. Among the three different endometriotic lesions, the highest IL-8 mRNA expression density was found in RPL(red peritoneal lesion), while the lowest IL-8mRNA expression density was detected in ULN(uterosacral ligament module).(3) There was a dose-dependent stimulatory effect of IL-8 on the survival of ESC. At 1ng/ml, anti-IL-8 significantly inhibited the survival of endometrial cells.Conclusion:IL-8 may be one of the essential factors for the pathogenesis of endometriosis.