The present investigation was conducted to evaluate the potential for the transfer of deoxycorticosterone (DOC) and deoxycorticosterone sulfate (DOC-SO4) from the fetal to the maternal compartment in near-term human pregnancy. To do so we measured progesterone, DOC, and DOC-SO4 in maternal venous serum and in umbilical arterial and venous sera. The levels of DOC and DOC-SO4 in maternal serum were significantly correlated to each other and to those of progesterone in maternal serum. However, there was no correlation between the levels of DOC or DOC-SO4 in umbilical arterial or venous sera and those of these steroids in maternal serum. Although there was no difference in the concentrations of DOC in umbilical arterial or venous serum, there was a highly significant difference in the umbilical arterial and venous concentrations of DOC-SO4. We conclude that the potential exists for DOC-SO4 from umbilical arterial plasma to enter trophoblasts where it could be hydrolyzed to DOC. The DOC so formed could then be redistributed primarily to the maternal but also to the fetal compartment.