Early and certain diagnoses of endometriosis are mandatory to begin the correct treatment and to exclude the risk of endometriosis-associated ovarian carcinoma (EOC) and endometrial stromal sarcoma (ESS). PURPOSE OF THE STUDY: To assess the immunohistochemical expression of Ber-Ep4, an epithelial antigen, and CD10 in endometriosis. MATERIALS AND METHODS: Forty-eight women underwent laparoscopic surgery for endometriosis and endometriotic samples were recovered for histology. In all surgical specimens Ber-Ep4 and CD10 were searched by an immnohistochemical method. The authors evaluated the correlations among the immunohistochemical positivity and the location of endometriosis. RESULTS: Most cases (40/48 83.34%) were represented by ovarian endometriotic cyst. Among the eight remaining cases, three (3/48, 6.25%) were pelvic endometriotic lesions, two (2/48, 4.17%) peritoneum of vesico-uterine pouch, one vaginal lesion (2.08%), one salpinx lesion (2.08%), and one inguinal location (2.08%). Ber-Ep4 and CD10 were expressed in 90% and in 100% of the ovarian lesions, respectively. In pelvic lesions Ber-Ep4 and CD10 showed both 66.67% of positivity and had the same pattern in peritoneal, salpinx, vaginal, and inguinal lesions (50%, 100%, 100%, 100%, respectively). Ber-Ep4 was negative in 6/48 (12.5%) cases whereas CDO10 was negative in 2/48 (4.17%) cases of endometriosis. The sensitivity of Ber-Ep4 and CD10 for endometriosis diagnosis were 87.50% and 95.83%, respectively. Immunohistochemistry for Ber-Ep4 showed positivity in all cases of endometriosis with typical cubic epithelium, whereas CD10 was positive in 1/2 (50%) atypical case.