OBJECTIVE: Endometriosis is a common gynecologic disorder in which the concentration and activation of peritoneal macrophages are increased. The goal of this study was to quantify pelvic fluid concentrations of two cytokines involved in macrophage recruitment and activation. STUDY DESIGN: A case-control study of women undergoing pelvic surgery was conducted by collecting peritoneal fluid from 12 women without evidence of endometriosis (controls), 12 with mild, and 12 with moderate to severe endometriosis. Concentrations of RANTES and interferon gamma, soluble cytokines known to recruit and activate macrophages, were quantified by enzyme-linked immunosorbent assays. RESULTS: Pelvic fluid concentrations of RANTES are elevated in women with endometriosis and the levels correlate with the severity of disease. By contrast, concentrations of interferon gamma appear unaffected by the presence of or severity of endometriosis. CONCLUSION: The findings indicate that RANTES, a cytokine with potent chemotactic activity for human monocytes, may play an important role in the recruitment of peritoneal macrophages in endometriosis.