In order to research into the relationship between atrial natriuretic peptide (ANP), aldosterone (Aldo) and pregnancy-induced hypertension (PIH), as well as normal pregnancy, the plasma concentrations of ANP and Aldo from normal pregnant women. PIH patients and their fetuses were measured by radioimmunoassay. It was found that maternal venous Aldo and ANP were higher in normal pregnant women than those in non-pregnant women. The plasma ANP was higher in PIH patients than that in normal pregnant women while plasma Aldo was lower. The plasma concentration of ANP was higher in the fetuses of PIH patients than that in the normal controls, but Aldo was lower. It is concluded that ANP concentration correlates significantly to the severity of PIH, and may be used for an early diagnosis of PIH.