IN THE course of the past year it has been demonstrated that the isolated perfused adrenal gland is capable of specific oxygenation of the steroid molecule in the carbon-11 position. Perfusion of the intact beef adrenal with serum or whole blood in the presence of adrenocorticotrophic hormone results in the appearance in the perfusate of pronounced adrenal cortical hormone activity (Hechter, 1949). Studies in which 11-desoxycorticosterone, 17-hydroxy-l11-desoxycorticosterone and androsterone were added to the perfusing fluid resulted in the specific oxidation of the steroids at the carbon-11 position, forming corticosterone, 17-hydroxycorticosterone and 11-(β)-hydroxyandrosterone respectively (Hechter, Jacobsen, Jeanloz, Levy, Marshall, Pincus and Schenker, 1949 and 1950). As a result of these studies by the Worcester group, the idea has arisen in a number of laboratories including our own, that oxidation of the steroid molecule at carbon-11 might be accomplished by the use of homogenates and perhaps cell-free extracts of adrenal tissue.