Abstract: After iv injection of dihydroepiandrosterone sulfate (DHA-S) at 20 or 40 mg/kg to female rats on day 19 of gestation, the tension and hydroxyproline level of uterine cervix were decreased obviously. However, DHA-S at 10 mg/kg showed no effect on the tension of uterine cervix. DHA-S in vitro, at 0.1 mg/kg significantly increased estradiol secretion in the ovaries and placenta of late pregnant rats.