Objective: To analyze current literature data on the etiology, diagnosis, and treatment of thin endometrium and to identify the relationship between endometrial thickness and pregnancy rate in the assisted reproductive technology (ART) program. Materials and methods: The PubMed and Cochrain Library databases over the past few years were analyzed to make a review. Results: The paper presents modern ideas on the etiology, diagnosis, and treatment of thin endometrium, as well as on the role of endometrial thickness in the onset of pregnancies in ART programs, as evidenced by Russian and foreign literature. Until now, many studies are contradictory and controversial, which cannot reach a consensus on the thin endometrium. This issue is still relevant and further multicenter studies will be able to approximate to the unraveling and solving of the problem. Conclusion: The endometrial thickness is one of the main risk factors for implantation failure in IVF, so physicians of different specialties are studying this topical issue to have positive results. There is a need for further investigations in this area, including those of the morphological, immunohistochemical, and molecular genetic characteristics of the endometrium, which will be able to improve the outcomes of ART in the presence of thin endometrium. © Aryutin D.G., 2023.