The association of some cases of endometrial carcinoma (EC) with hyperestrogenism is well known. The prognostic significance of concomitant endometrial hyperplasia (EH) in EC were evaluated in 142 patients with clinical stage I EC in whom lymph node assessment was carried out in 121 patients. The presence of EH was significantly associated with better differentiated tumor having lesser degrees of myometrial invasion, low segment-adnexal-lymphovascular space and pelvic/para-aortic lymph node involvement. However, the presence of EH was not significantly associated with the less virulent histologic subtypes. The possible existence of two types of EC--a hormonal-dependent EC associated with EH, and an independent EC not associated with EH--is discussed and the prognostic significance of concomitant EH stressed.