Cortisol (F), Cortisone (E) and dehydroepiandrosterone sulfate (DHAS) were determined in maternal peripheral plasma and umbilical cord plasma between 21 and 30 weeks of amenorrhea. In fetal plasma, DHAS levels were the highest and those of F the lowest. E always exceeded F. The pattern of all these steroids was characterized by a plateau throughout the period considered. In maternal plasma, F levels were more elevated than those of E but lower than DHAS concentrations. All the steroids plateaued as in the fetus. The study of the correlation between the steroids in either the same milieu or in maternal and umbilical cord plasma demonstrated that fetal E was correlated with maternal F and with fetal F while fetal DHAS was inversely correlated with maternal E.