Objective: To study the effect of interleukin-8 (IL-8) and mouse anti-human IL-8 monoclonal antibody on endometrial stromal cell adhesion to fibronectin. Design: Prospective, controlled in vitro study. Setting: Academic research laboratory. Patient(s): Women undergoing benign gynecologic surgery for indications other than endometrial disease. Intervention(s): Endometrial stromal cells were treated with IL-8 and mouse anti-human IL-8 monoclonal antibody at different concentrations and adhesion assays were performed by labeling the cells with calcein. Main Outcome Measure(s): Fluorescence in calcein-labeled endometrial stromal cells. Result(s): IL-8 induced a concentration-dependant increase of cell adhesion to fibronectin matrix (twofold at 10 ng/mL; P=.006). Treatment of endometrial stromal cells with anti-IL-8 neutralizing antibody inhibited partially the cell adhesion. Conclusion(s): IL-8 stimulates the adhesion of endometrial stromal cells to fibronectin in a concentration-dependent manner. IL-8 may thus be relevant for the attachment of endometrial implants in the pathogenesis of endometriosis. (C) 1999 by American Society for Reproductive Medicine.