Incubation of DCA with minced adrenal tissue resulted in an increase of gluco-corticoid activity. The conversion percentage was about 12·5 %, when the inherent small gluco-corticoid activity of DCA was allowed for. Boiling the adrenal mince inactivated the enzyme responsible. The addition of ascorbic acid had no effect on the conversion reaction. The incubation of cortisone acetate with adrenal mince led to no alteration in its gluco-corticoid activity. The incubation of DCA with minced corpus luteum tissue also resulted in an increase of gluco-corticoid activity, but the conversion percentage was only 25 % of that of the adrenal. Incubation with other tissues or plasma showed no significant change. Biological tests on extracts of fresh non-incubated corpora lutea and placenta revealed no gluco-corticoid activity. The combined administration of ascorbic acid and DCA to fasted adrenalectomized mice showed no enhancement in glycogen deposition. The incubation of cholesterol with adrenal tissue did not result in an increase of gluco-corticoid activity.