The implantation rate after frozen-thawed embryo transfer cycles depends mostly on the receptivity of the endometrium and the embryo quality.The effects of human chorionic gonadotropins (hCG) on the endometrium have been investigated for several years. hCG was shown to up-regulate gene expression during the differentiation of human endometrial stromal cells into decidua. The aim of our study was to assess the benefit of hCG supplementation throughout the secretory phase of artificial frozen-thawed embryo transfer cycles.