Propranolol was infused intravenously for 60 minutes to five ewes (4 mug per kilogram per minute) or five fetal sheep (10 mug per kilogram per minute). The umbilical blood flow was significantly decreased by 18 per cent from control at 60 minutes with either maternal or fetal propranolol infusion. Uterine blood flow and maternal and fetal mean arterial pressure did not significantly change. Maternal and fetal heart rates decreased 18 and 9 per cent from control, respectively, during maternal propranolol infusion. With propranolol to the fetus, fetal heart rate decreased 15 per cent and maternal heart rate did not change. During all infusion, maternal and fetal arterial pH, PCO2 and PO2 remained within normal physiologic limits.