Vehicle or 8 or 16 mg PGF2 alpha/58 kg/body weight (BW) was given intramuscularly to intact, hysterectomized and ovariectomized 90 to 100 day pregnant ewes in three separate experiments. Hysterectomy alone decreased (P < or = 0.05) estradiol-17 beta in jugular venous blood by 80 percent within 16 hours and profiles of estradiol-17 beta did not differ (P > or = 0.05) among vehicle or 8 or 16 mg PGF2 alpha/58 kg/BW-treated ewes. Profiles of estradiol-17 beta differed (P < or = 0.05) in intact pregnant ewes treated with 8 or 16 mg PGF2 alpha/58 kg/BW when compared to controls and in ovariectomized (P < or = 0.10) 90 to 100 day pregnant ewes treated with 16 mg PGF2/58 kg/BW. Estradiol-17 beta decreased (P < or = 0.05) over time in vehicle and 8 mg PGF2 alpha/58 kg/BW-treated intact and in vehicle-treated ovariectomized 90 to 100 day pregnant ewes. Cortisol decreased (P < or = 0.05) over time in hysterectomized, intact, and ovariectomized 90 to 100 days pregnant ewes, but did not differ (P < or = 0.05) among vehicle or 8 or 16 mg PGF2 alpha/58 kg/BW-treated ewes. It is suggested that estradiol-17 beta has a role in regulating ovine placental steroidogenesis.