Objective: To show the existence and density of endometrial nerve fibers in endometriosis and other gynecological pathologies and their relation to pain. Methods:This cross-sectional study involved 325 women planned to have gynecologic surgeries at Ain Shams University Maternity Hospital from December 2010 to February 2014. The diagnosis was adenomyosis, uterine fibroid, endometrial hyperplasia or carcinoma, polycystic ovarian syndrome (PCOS), ovarian tumors and endometriosis. Endometrial tissue was obtained during hysterectomy or with a curette and then immunostained with the pan neuronal marker anti PGP 9.5 to detect the endometrial nerve fibers and to quantify their density if present.Results: Endometrial nerve fibers were detected in all cases of endometriosis and 13.7% of other pathologies except PCOS (p<0.001). Pain was the only independent factor associated with the presence of endometrial nerve fibers (OR 14.5; 95%CI: 6.7-31.2). Type of pain was not related to the presence of endometrial nerve fibers (p=0.668). The nerve fiber density is strongly correlated with pain scores (r=0.479, p<0.001).