The purpose of the present study was to investigate whether placental immunohistochemical adrenomedullin expression in normal normotensive pregnancies is different from that in pregnancies with pre-eclampsia. Placental tissues were obtained from seven normal normotensive pregnancies and 12 pregnancies with pre-eclampsia. The intensity of adrenomedullin staining in syncytiotrophoblasts was evaluated by means of immunohistochemistry and the ratio of the number of intact tertiary villi to that of total tertiary villi (intact/total villi ratio) was determined. The intensity of adrenomedullin expression in the placenta obtained from pregnancies with pre-eclampsia was significantly decreased compared with expression in placentas from uncomplicated normotensive pregnancies (P < 0.005). The intact/total villi ratio in placentas obtained from pregnancies with pre-eclampsia was significantly lower than that in placentas from normal normotensive pregnancies (P < 0.0001). In the amnion and extravillous trophoblast cells in both groups, no difference for the intensity of adrenomedullin expression was noted. These results suggest that adrenomedullin synthesis in the villous syncytiotrophoblasts is decreased in pregnancies with pre-eclampsia.