Abstract: Objective：To investigate the expression of protein gene product 9.5 （PGP 9.5） in situ function layer and ectopic endometrium of endometriosis，and observe the relationship of the expression of PGP 9.5 and the pelvic pain. Methods：44 endometriosis patients enrolled in this study （pain group 28 cases，without pain group 16 cases），to detect the expression of PGP 9.5 in situ function layer and ectopic endometrium of patients were determined by immunohistochemical methods of Envision TM，20 patients with uterine fibroid without pelvic pain were included as the control group. Investigate the relationship of PGP 9.5 in endometriosis and the PGP 9.5 and the pelvic pain. Results：The positive rate of PGP 9.5 expression in endometriosis group situ function layer was 72.9%，and the positive rate of PGP 9.5 expression in control group situ function layer was 25.0%，which has significant difference （P＜0.05）. The positive rate of PGP 9.5 expression in EMs group ectopic endometrium was 81.8%，and the positive rate of PGP 9.5 expression in endometriosis pain group ectopic endometrium was 92.9%，compared with the without pain group 62.5%. Which has significant different （P＜0.05）. EMs in ectopic group and ectopic endometrial nerve fiber density were higher than control group （all P＜0.01）. The expression of PGP 9.5 has nothing to do with the staging and location of the EMs （all P＞0.05）. EMs patients′ pain has nothing to do with the lesion location （P＞0.05），and has nothing to do with the density of nerve fibers （P＞0.05）. Conclusions：The expression of PGP 9.5 had a significant increase in the endometriosis situ function layer and ectopic endometrium. At the same time，its increased expression had a close relationship with the pelvic pain.

Key words: Endometriosis, Endometrium, Neuropeptides