Dramatic advances in assisted reproductive technologies have greatly improved the pregnancy rate for infertile couples. Recently, however, the recent pregnancy rates and live-birth rates have not significantly increased, mainly because there are very few effective treatments available for implantation failure and subsequent early pregnancy loss. Successful implantation requires good embryo quality, appropriately timed and arranged endometrial receptivity, and the efficient crosstalk between the embryo and the receptive endometrium. It is thought that impairment of any one of these factors or biological processes may result in implantation failure. In this review article, I have focused on endometrial dysfunction as a cause of implantation failure, and discuss its possible etiologies and therapeutic strategies.