In 1930 Engelhart reported the preparation of lipoid extracts from adrenal glands, which produced oestrous and progestational effects in the uterus of the immature rabbit. These findings were confirmed by Callow & Parkes [1936], who showed that the active principles could be separated by the method of Allen & Meyer [1933]. In 1938 the isolation of progesterone, together with 3:20-allo-pregnanolone, was announced [Beall & Reichstein, 1938; Beall, 1938]. Oestrone has now been isolated from two ox adrenal concentrates. A preliminary report of this work appeared last year [Beall, 1939]. By the courtesy of N. V. Organon, Oss, Holland, two adrenal concentrates, both possessing a marked oestrogenic activity, were placed at the disposal of Dr. A. S. Parkes and made available to the author. As a preliminary step, the first concentrate was saponified with hot alcoholic potash, the greater part of the oestrogenic activity appearing in the alkali-soluble fraction.