Implantation refers to a series of interactions between embryo and endometrium including hatching, attachment, and outgrowth. We investigated the expression and function of beta1 integrin and focal adhesion kinase (FAK) in human decidual cells during implantation. Immunofluorescent staining localized beta1 integrin to surfaces of cultured decidual cells. Double staining for beta1 integrin and mediators of intracellular signaling involving beta1 integrin, such as FAK and vinculin, colocalized beta1 integrin with these substances, suggesting that human decidual cells express beta1 integrin in the focal adhesion region. We next investigated the actions of beta1 integrin and FAK in implantation by co-culturing mouse embryos and human decidual cells. Mouse blastocysts attached to cultured decidual cells after embryo hatching, usually within 24 h of culture initiation. Blastocysts attached to decidual cells exhibited extensive outgrowth at 48 h. Treatment of decidual cells with an antibody against beta1 integrin or with an antisense FAK oligonucleotide did not affect hatching or attachment of blastocysts, but either one could inhibit outgrowth. Thus, it was concluded that human decidual beta1 integrin and FAK participate in this final step of implantation.