Objective: Superovulation in human and animals induces by gonadotropins follicle stimulating hormones (FSH) for production of more mature follicles. Gonadotropins will affect sex steroid hormone production that will control immune responses in uterus through steroid hormone receptors. Some evidences show that TLR expression varies during menstrual cycle and can be regulated by steroid hormones. Since TLR-4 expression and its activity is important in health and inflammatory condition of the uterus for embryo receptivity and endometrial disorders, we designed the present experiment for determining the effect of superovulation on TLR-4 expression in mouse model. Materials and Methods: Female BALB/C mice (6 weeeks) were superovulated by peritoneal injection of PMSG (pregnant mare serum gonadotropin) at day 0 and HCG 48 hours later. One, two, three, four and five days after HCG injection five mice were euthanized and their uterus separated from other part of reproductive organ. Uterus were transferred to cryotubes and preserved at -196°C. After collection of all samples, RNA extraction was performed and TLR-4 RNA expression was measured by real time PCR method. Results: According to real time PCR results we found that TLR-4 increased significantly (p≤0.05) during 2 days post HCG injection in treated BALB/C mice compared to non hormone treated mice. This increase in TLR-4 RNA expression will decrease gradually from day 2 to day 5 post HCG injection to the same level of non treated mice. Conclusion: Toll like receptors as one of the innate immune receptors , have important roles in defense against pathogens in uterus but their activity may interfere with appropriate cytokine milieu for embryo implantation and pregnancy. So the balance in TLR expression during menstrual cycle and pregnancy is important. Hormone treatment can change the balance through its inhibitory or inducibility effect on TLRs. Our results show that although superovulation induces TLR4 expression but it will decrease to normal level before implantation time in uterus. So it seems that superovulation have no effect on endometrial disorders that happen in response to TLR4 induced inflammation.