Plasma endothelin (ET) level during pregnancy and postpartum period were measured in 57 women including 41 cases of pregnancy-induced hypertension (PIH) by radioimmunoassay (RIA), and ET in their fetal cord vessels were determined as well. The results showed that ET level of normal pregnant women was significantly higher than that of normal non-pregnant controls. ET level in PIH patients was significantly higher than that of the normal pregnant women and was positively related to the severity of PIH, and returned to non-pregnant status in postpartum period. It indicated that ET might play an important role in the pathogenesis of PIH.