Estrogen and progesterone regulate HOXA10 expression in the endometrium, where HOXA10 is necessary for implantation. The integrins are also involved in early embryo-endometrial interactions. Here we show that HOXA10 directly regulates β₃-integrin subunit expression in the endometrium, likely mediating the effect of sex steroids on β₃-integrin expression. β₃-Integrin expression was decreased in endometrium shown to have low HOXA10 expression. β₃-Integrin mRNA levels were increased in endometrial adenocarcinoma cells (Ishikawa) transfected with pcDNA3.1/HOXA10, and decreased in cells treated with HOXA10 antisense. Seven consensus HOXA10 binding sites were identified 5′ of the β₃-integrin gene. Direct binding of HOXA10 protein to four sites was demonstrated by EMSA. Reporter gene expression increased in BT-20 cells cotransfected with pcDNA3.1/ HOXA10 and pGL3-promoter vector containing region F (encompassing all seven HOXA10 consensus sites). A 41-bp segment (Region A) showed highest affinity binding to HOXA10 protein. Increased reporter expression, equal in magnitude to that obtained with Region F, was obtained with Region A. HOXA10 protein binding within Region A was localized by deoxyribonuclease I footprinting. β₃-Integrin expression was directly up-regulated by HOXA10 through a 41-bp 5′-regulatory element. Sex steroids regulate the expression of endometrial β₃-integrin through a pathway involving HOXA10.