The intravenous injection of adrenaline simultaneously with 1 i.u. of Pitocin in the sow caused a marked reduction in the amount of milk that is normally ejected following the injection of 1 i.u. of Pitocin alone. In each sow a plateau was reached with a dose of approximately 400 μg. of adrenaline, and an increase in the amount of adrenaline injected up to 2000 μg. did not cause any further reduction in the amount of milk ejected. The injection of 1000 μg. adrenaline, 62 to 90 secs, before the injection of 1 i.u. of Pitocin, completely inhibited the ejection of milk associated with the latter. In two out of three sows a definite, though small, ejection of milk occurred following the injection of either 400 or 1000μg. of adrenaline alone. The possible actions of adrenaline in these experiments are discussed.