Abstract: Objective To investigate the role of serum epithelial neutrophil-activating peptide-78 (ENA-78) in the pathogenesis of endometriosis. Methods Serum concentrations of ENA-78 were measured by means of enzyme-linked immunosobent assay (ELISA) in 42 patients with endometriosis (20 in stages Ⅰand Ⅱ and 22 in stages Ⅲ and Ⅳ) in comparison with 25 women without endometriosis (control group). Results Serum concentrations of ENA-78 were significantly higher in endometriosis group than in the control group (2.97±1.91 ng/ml vs 0.72±0.24 ng/ml, P<0.001), and ENA-78 levels in stages Ⅲ and Ⅳ were significantly higher than those in stagesⅠ and Ⅱ (4.48±1.25 ng/ml vs 1.30±0.74 ng/ml, P<0.001). Significant difference in ENA-78 levels between follicular phase and luteal phase was found in neither of the groups. Conclusion Patients with endometriosis have elevated serum ENA-78 levels, which might be a pathogenic factor of endometriosis.