A RECENT communication by Boe et al.1 on adrenocorticotropic hormone in the whale prompts us to communicate our own preliminary results on the isolation of this hormone from whale pituitaries. We, however, used the anterior lobe of the whale gland only, and obtained, by Lyons's well-known acid acetone extraction procedure2, from 1 kgm. of the frozen glands from mixed blue, fin and humpback whales, with blue and fin predominating, 4.0 gm. of the so-called ‘crude prolactin’. A preliminary purification of this preparation was possible by simple reprecipitation from acid aqueous acetone solution, followed by Chamberland filtration of the watery solution of the precipitate thus obtained, and finally by lyophilizing the resulting clear extract. In this manner, 0.9 gm. of a whitish, easily soluble powder was obtained, which, when assayed by the ascorbic acid depletion method of Sayers3, showed an adrenocorticotropic activity nearly equal to that of the Armour La-1-A standard, and was completely free from pressor activity (posterior lobe hormone).