THE adrenal gland produces a hormone which is essential to life. During the last two years, several workers have succeeded in isolating, from purified preparations of the cortical hormone, a number of crystalline compounds. Among these substances corticosterone and dehydro-corticosterone possess the greatest biological activity. The structures (I) and (II) were proposed for corticosterone and its dehydroderivative1,2. These formulae were not definitely proved, but were chiefly based on the assumption that corticosterone might possess a constitution similar to some of the above-mentioned compounds, which have been isolated from the adrenal gland and which have been found to contain one more atom of oxygen in their molecules. These substances, which can be designated as the C21-O5-group, contain the sterol ring-system since they can be converted into the hydrocarbon androstane3. The suggestion that corticosterone contains the same ring-system has so far not been supported by any experimental evidence.