This chapter describes the principal putative causes of implantation failure and reviews therapeutic strategies. Recurrent implantation failure is a significant and distressing clinical problem. Adjuvant medical therapies to those required for ovarian hyperstimulation are frequently applied for improving embryo implantation and particularly when the clinician is faced with recurrent implantation failure. The appropriate management of the medically complicated patient presenting for in-vitro fertilization (IVF) can be complex and often requires an interdisciplinary approach. Standard ovarian hyperstimulation and the resultant supraphysiological estradiol levels have been shown to impact negatively on endometrial receptivity and embryo quality. Studies of mild ovarian stimulation regimens have shown encouraging results. Although fewer embryos are obtained, an increased percentage of euploid embryos per number of oocytes retrieved have been reported. Significant improvements in clinical pregnancy rates can be achieved by giving due attention to embryo transfer technique.