Abstract: The aim of this study was to investigate whether the endometrium of women with unexplained infertility differs in the presence of the beta 3 (β3) integrin molecule from the endometrium of normal fertile women. In a retrospective case-control study 30 endometrial biopsies from hysterectomies with nonendometrial pathology and 30 endometrial samples from women with a history of unexplained infertility were collected during the window of implantation. Immunohistochemically staining with a monoclonal antibody against β3 integrin subunit in endometrial biopsies was performed and then assessed semiquantitively by microscope on different endometrial compartments including glandular epithelial cells, vessels, lymphocytes, macrophages and stromal cells. Chi-square test was used to compare the expression and defect of β3 integrin subunit between two groups. The results showed that β3 integrin molecules were present in fertile and infertile endometrial uterine tissues. The majority of glandular epithelial cells expressed β3 integrin in fertile endometrium. However, the endometrial expression of β3 integrin was reduced significantly in infertile endometrium during the window of implantation (p<0.05). A few numbers of vessels and stromal cells expressed β3 integrin molecule with no statistical significance between the two groups. In conclusion Abnormal endometrial integrin expression is a frequent finding in women with unexplained infertility. A therapeutic potential approach in improving uterine endometrium receptivity together with up-regulation of β3 integrin in this population of women suggested.