Objective: The presence of the various cytokines in human peritoneal fluid has been evaluated incompletely. Changes in cytokine levels may be related to activation of peritoneal macrophage and T-lymphocyte, development of endometriosis, and infertility. This study assesses peritoneal fluid levels of interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10) and tumor necrosis factor-${alpha}$ (TNF-${alpha}$) in infertile women with endometriosis and normal women without endometriosis. Design: Prospective and case-control study in university hospital. Materials and Methods: Cytokine levels in peritoneal fluid obtained during laparotomy or laparoscopy from 21 patients in infertile patients with endometriosis and 24 controls undergoing laparotomy or laparoscopy with no evidence of pelvic endometriosis were determined by enzyme-linked immunosorbent assay. Results: The mean levels of interleukin-6 in infertile patients with endometriosis and controls were $72.7{pm}23.7$ pg/ml and $18.5{pm}9.7$ pg/ml respectively (p=0.02). Similarly, the mean levels of interleukin-8 in infertile patients with endometriosis was significantly higher than that of controls ($445.0{pm}89.6$, vs $45.1{pm}48.4$, p=0.04). The mean concentration of interleukin-10 in infertile patients with endometriosis was significantly lower than that of controls ($1.09{pm}0.04$ vs $2.19{pm}0.03$, p=0.03). The level of tumor necrosis factor-${alpha}$ was not significantly different between the two study groups. Conclusions: Increased IL-6 and IL-8 and decreased IL-10 levels in the peritoneal fluid may be related to pathogenesis in the endometriosis and infertility, suggesting that partially contribute to the disturbed immune regulation observed in infertili women with endometriosis.