['To investigate the presence of interleukin-8 (IL-8), a macrophage-derived angiogenic factor, in peritoneal fluid (PF) of women with and without endometriosis.', 'Case-control study.', 'University hospital.', 'Eighteen women with laparoscopic findings of mild to severe endometriosis, and nine women with no visual evidence of pelvic pathology.', 'Peritoneal fluid IL-8 levels were determined using an ELISA. Interleukin-8 concentrations were compared among women with and without endometriosis. Correlation between PF IL-8 concentration and endometriosis stage was investigated.', 'Interleukin-8 was detectable in the PF of a majority of women (67%). Interleukin-8 concentrations were higher in the PF of women with endometriosis than in matched normal controls. A significant correlation between PF IL-8 concentration and endometriosis stage was noted.'] Are interleukin-8 concentrations elevated in peritoneal fluid of women with endometriosis?