Abstract: Embryo implantation failure is one of major factors related to the clinical outcomes of in vitro fertilization-embryo transfer（IVF-ET）, even if the good-quality embryos were transferred, which may be related with the aberrant endometrial microenvironment. The chronic endometritis（CE）, a subtle lesion and persistent inflammation without clinical symptom or only accompanied by mild disturbances and increased leucorrhea, is found by the widespread hysteroscopy test, which cannot be diagnosed in some infertility women by routine ultrasound and hysteron-salpingography（HSG）. The effect of CE on the clinical outcomes of IVF-ET has widely been paid attention. It was found that CE was associated with the repeated implantation failure after IVF-ET. The histological test is the gold standard for CE diagnosis, and anti-infective therapy could be effective for those patients with CE.

Key words: Fertilization in vitro, Embryo transfer, Endometritis, Hysteroscopy, Embryo implantation