Abstract Objective: To investigate the expression of α4 and β3 integrin subunit levels in the endometrium of healthy women and copper intrauterine device (IUD) T200 users. Design: Case control study. Setting: An academic teaching hospital and a primary care clinic. Patient(s): Thirteen copper IUD users and 13 normal fertile women. Intervention(s): Timed endometrial biopsies during the mid-secretory phase (days 20 to 24). Main Outcome Measure(s): Histologic dating of endometrium and immunohistochemical staining intensity of α4 and β3, using the semiquantitative immunohistochemical score (HSCORE). Result(s): All endometrial biopsies consistent with menstrual dates were examined for integrin expression (β3 and α4). No difference in α4 integrin expression was found between IUD users and controls in both luminal and glandular epithelium. In fertile controls, αvβ3 staining was present in 100% and 38.4% of glandular and luminal epithelium, respectively. In contrast, only 61.5% of the IUD users had any αvβ3 staining in the glandular epithelium and only 53.9% in the luminal epithelium. The intensity of immunoreactivity between the two groups (mean HSCORE) did not differ significantly. Conclusion(s): Proportionately, significantly fewer women using copper IUD had positive αvβ3 immunoreactivity in the glandular epithelium of mid-secretory endometrium.