Term and preterm cervical ripening and dilatation have similarities with an inflammatory reaction. Since cell adhesion molecules are involved in this process, investigations on the expression of intercellular adhesion molecule-1, endothelial leukocyte adhesion molecule-1, vascular cell adhesion molecule-1, and platelet endothelial cell adhesion molecule in the lower uterine segment and in vitro experiments on human umbilical vein endothelial cells were performed. In addition, current reports on expression of endothelial adhesion molecules by the uterine cervix were summarized. Cell adhesion molecule expression by lower uterine segment and uterine cervix in term and preterm parturition was measured using immunohistochemistry, enzyme immunoassay, and Northern blot analysis. Regulation of adhesion molecule expression was evaluated in vitro by indirect immunofluorescence and flow cytometry using human umbilical vein endothelial cells. Investigations in term parturition revealed that intercellular adhesion molecule-1, endothelial leukocyte adhesion molecule-1, and vascular cell adhesion molecule-1 expression increases during parturition. In preterm labor, the expression of endothelial leukocyte adhesion molecule-1 and intercellular adhesion molecule-1 in the lower uterine segment increased. Expression of platelet endothelial cell adhesion molecule did not change in term and preterm parturition. Expression of adhesion molecules was localized mainly on lower uterine segment vascular endothelial cells and to a smaller extent on leukocytes. In vitro experiments showed that expression of adhesion molecules by human umbilical vein endothelial cells can be stimulated by tumor necrosis factor-α, 17β-estradiol, prostaglandin E2, and the antigestagen onapristone. Progesterone exerted no stimulatory effect. Cervical ripening and dilatation during term and preterm parturition are associated with an increased expression of endothelial cell adhesion molecules by lower uterine segment and uterine cervix. The expression can be modulated by pro-inflammatory cytokines, sex hormones, and prostaglandin E2. Mechanisms controlling the extravasation of leukocytes may play a fundamental role in term and preterm parturition. Microsc. Res. Tech. 60:430–444, 2003. © 2003 Wiley-Liss, Inc.