Three cell surface peptidases have been shown to be present in the human endometrium. Aminopeptidase N and neutral endopeptidase are detected on the endometrial stromal cells and decidual cells, while dipeptidyl peptidase IV is detected on the endometrial glandular cells and surface epithelium. As these cell surface peptidases can degrade a variety of biologically-active peptides including cytokines and growth factors, they are considered to be involved in the local metabolism of these molecules. In addition, recent studies have indicated that they are involved in local immune responses, cell attachment, and cellular maturation/ differentiation of endometrial cells, and suggest an important role of these endometrial cell surface peptidases in implantation processes.