BACKGROUND: Although the etiology of endometriosis is not well understood, chemokines and their receptors are believed to play a role in its pathogenesis. Therefore, we aimed to investigate the expression and localization of interleukin-8 (IL-8) receptors CXCR1 and CXCR2 in eutopic and ectopic endometrial tissues of women with endometriosis, and in endometrium of women without endometriosis. METHODS: Ectopic (n=27) and homologous eutopic endometrium (n=25) from women with endometriosis and endometrium from women without endometriosis (n=27) were used for immunohistochemical analysis of CXCR1 and CXCR2. RESULTS: In normal endometrium, epithelial CXCR1 and CXCR2 immunostaining intensities were similar in the proliferative and secretory phase. Stromal CXCR1 expression was less then epithelial expression and did not show cyclical difference. No stromal CXCR2 expression was observed. In eutopic endometrium of women with endometriosis compared to endometrium of women without endometriosis, there was a significant increase in both proliferative and secretory phases for epithelial CXCR2 expression, and in proliferative phase for CXCR1 expression (P<0.05). Both receptor immunoreactivities were significantly increased in the epithelial cells of ectopic endometrial tissues compared to that of normal endometrium (P<0.05). CONCLUSIONS: These findings suggest that IL-8 and its receptors may be involved in the pathogenesis of endometriosis.