The fetoplacental unit of the ewe is capable of increasing the biosynthesis of estrogens following the exogenous administration of DHEA to the fetus. The maximum concentrations of estrogens appeared approximately 30 minutes after the administration of DHEA. Uterine blood flow in the pregnant ewe increased approximately 90 minutes after the maximum concentrations of estrogens were noted. The administration of DHEA to the nonpregnant, ovariectomized ewe did not elicit estrogen biosynthesis or changes in uterine blood flow. Isotope experiments in the pregnant ewe demonstrated the incorporation of DHEA into urinary estradiol.