A role for the EGF system, in particular HER1 and 2, in growth of the endometrium has been suggested but HER1 and 2 have not been studied in all locations of endometriosis and in ovarian endometrioid adenocarcinoma (OEC) which is a rare form of malignant transformation of endometriosis. Immunohistochemistry (IHC) was used for studying HER1 and HER2 in ovarian (n = 10), peritoneal (n = 10), colorectal endometriosis (n = 20) and OEC (n = 10). Fluorescent in situ hybridisation (FISH) was used for analysing the status of HER2 gene in colorectal endometriosis and OEC. All samples were negative for HER2 in both glandular and stromal cells and in glandular cells for HER1 by IHC. In 15 out of 20 colorectal endometriosis, there was a weak expression in stromal cells. Following FISH, two colorectal samples had a partial 17 aneusomy and three OEC, a 17 polysomy. The other samples were 17 disomic without HER2 amplification; HER1 and 2 do not seem to have a role in endometriosis physiopathology.