Endometriosis is a disease that affects about 5% of women of reproductive age, but is found much more frequently in those with pelvic pain and/or infertility. In affected individuals, shed endometrium is thought to attach and spread within the pelvis through specific cell adhesion receptors. To understand why some women develop endometriosis while others do not, researchers have begun to examine these receptors and their extracellular matrix ligands. Cell adhesion molecules fall into 4 major groups including cadherins, selectins, members of the immunoglobulin superfamily, and integrins. Based on our current understanding, each may potentially play a role in the development or progression of this disease. In addition, the use of integrins as markers of the normal endometrial phenotype may be useful for the diagnosis of endometriosis and may identify women with defects in endometrial function leading to infertility or recurrent pregnancy loss. As more information becomes available, it may be possible to develop better treatments for endometriosis based on these concepts and to identify those women at risk for development of this common yet serious disorder.