Blood pressure and heart rate response to pharmacologic autonomic blockade were studied in the 31 fetuses of 27 time-dated pregnant sheep from 85 to 150 days of gestation and in 5 neonatal lambs. A fetal hind limb vein and either a femoral or carotid artery were cannulated and following at least 2 days’ recovery from surgery, the fetuses were studied over several days while the ewes stood undisturbed. The degree of control exerted by the autonomic nervous system in the fetus was examined by selective blockade of parasympathetic, and of α- and β-adrenergic, components. Evidence of autonomic activity was found at all ages studied, and the responses of late gestation fetuses and of the neonates were similar. Whereas parasympathetic and α-adrenergic blockade produced a maximum response by 120 days’ gestation with little further change, β-adrenergic response increased significantly during late gestation.