To detect the oxytocin receptor (OTR) expression levels in the endometrium and decidua from women who have experienced recurrent implantation failure (RIF) and fertile women.Laboratory study using human endometrial and decidual samples.University-affiliated hospital.Six patients with RIF and six fertile women were recruited for endometrial sampling on day 20-24 of the menstrual cycle. Decidual tissues were collected from women who had a history of RIF and experienced a spontaneous abortion at 6-8 weeks of gestation (n = 8) and women with healthy pregnancies that terminated for nonmedical reasons (n = 8).None.OTR expression in the endometrial and decidual tissues was detected with the use of real-time quantitative polymerase chain reaction and Western blotting.OTR protein and mRNA were significantly increased in the endometria of RIF patients. In the decidua, OTR protein was significantly up-regulated in the RIF group, whereas mRNA was significantly decreased in this group.Women who experienced RIF presented with an aberrant expression pattern of OTR in the endometria and decidua.Copyright © 2020 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.