['To investigate the presence of epithelial neutrophil-activating peptide 78 (ENA-78) in peritoneal fluid of women with and without endometriosis and to identify the cells that produce this inflammatory protein.', 'Case-control study.', 'University hospital.', 'Eighteen women with and 9 women without endometriosis.', 'ENA-78 protein and mRNA levels were compared among women with and without endometriosis in samples of peritoneal fluid, samples of endometriotic lesions obtained by biopsy during laparoscopy, and peritoneal macrophages. Enzyme-linked immunosorbent assay, reverse transcription polymerase chain reaction, and in situ hybridization methods were used. Secretion of ENA-78 protein by interleukin-1beta-stimulated endometriotic stromal cells and in the media of lipopolysaccharide-stimulated peritoneal macrophages were compared to that in unstimulated cell cultures.', 'Peritoneal fluid concentrations of ENA-78 were significantly higher in affected women than in controls. Ectopic epithelial and stromal cells and peritoneal macrophages express ENA-78 messenger RNA. Interleukin-1beta stimulation of stromal cell cultures resulted in a 23-fold increase in ENA-78 concentration, and lipopolysaccharide stimulation of peritoneal macrophages increased concentrations by 8-fold.'] Are epithelial neutrophil-activating peptide 78 concentrations elevated in the peritoneal fluid of women with endometriosis?