Erythropoietin-producing hepatocellular receptor and its membrane-bound ligands (Eph-Ephrin) system could regulatesome mammalian blastocyst attachment and spreading. In order to investigate the involvement of the Eph-Ephrin systemin swine embryo attachment, mRNA expression of Eph-Ephrin molecules in endometrium was examined by real-time RTPCRduring embryo implantation in pigs. The results indicated that mRNA expressions of Eph A5, A7 and Ephrin A5 allcontinually increased from pregnancy day 13 to 24. Ephrin A3 mRNA expression significantly increased from day 13 to 18and decreased from day 18 to 24, and the expression was the lowest on pregnancy day 13 and the highest on day 18.However, Ephrin A4 mRNA expression was the lowest on pregnancy day 18 and the highest on day 24, and the expressiondecreased from day 13 to 18 and increased from day 18 to 24. Furthermore, mRNA expressions of Eph A5 and A7 were bothfound in other tissues, such as brain, muscle, intestine, stomach, etc. These findings suggest that the Eph-Ephrin systemmay play an important role in regulating the contact between blastocysts and endometrium during swine embryoimplantation.