en Original Article Original Article <strong>Background: </strong>The preparation of endometrium for embryo reception and implantation are controlled by ovarian hormones. These hormones have distinct cyclical changes during estrus cycle.<br> <strong>Objective: </strong>The aim of this study was to evaluate the changes in morphology and morphometrical indices of endometrium by daily injections of estrogen and progesterone in ovariectomized mouse.<br> <strong>Materials and Methods:</strong> In total 60 adult NMRI female mice were ovariectomized and after two weeks, they were randomly divided into five groups: control, sham group, estrogen treated mice (which received daily dosage of 0.5 ml/mouse of hormone for five days), progesterone treated mice (which received daily dosage of 0.2 ml/mouse of progesterone hormone for five days) and estrogen-progesterone treated mice (they received 0.5 ml/mouse estrogen on the first day and 0.2 ml/mouse progesterone injections from the second day to the fifth day of treatment). The mice were sacrificed in every day (n=5) up to five days after treatment and their uterine horns were obtained and processed for morphological and morphometrical studies.<br> <strong>Results: </strong>On the second day of treatment, the diameter of glands was observed to be more in the progesterone group (53.75&plusmn;6.32&mu;) than this in the estrogen (45.13&plusmn;7.78 &mu;) and estrogen-progesterone treated groups (48.17&plusmn;13.58 &mu;). While, the number of glands (76.25&plusmn;17.37) and thickness of endometrium (39.58&plusmn;3.37 &mu;) were observed to be more in the estrogen treated group (p=0.01).<br> <strong>Conclusion:</strong> Progesterone had effect on the gland whereas estrogen caused increased in height of surface epithelium of endometrium. Overall, the day 2 after treatment (in all experimental groups) is suitable day for sampling for further studies. Endometrium, Exogenous ovarian hormones, Ovariectomized mice, Morphometry, Morphology 125 0 http://ijrm.ir/browse.php?a_code=A-10-549-253&slc_lang=en&sid=1 Fatemeh Peyghambari No Department of Anatomy, Tarbiat Modares University, Iran Mojdeh Salehnia mogdeh@dr.com Yes Department of Anatomy, Tarbiat Modares University, Iran Mehdi Forouzandeh Moghadam No Department of Biotechnology, Tarbiat Modares University, Iran Mojtaba Rezazadeh Valujerdi No Department of Anatomy, Tarbiat Modares University, Iran Ebrahim Hajizadeh No Department of Biostatistics, Tarbiat Modares University, Iran