In the second paper of this series [Cowie & Folley, 1946a] we have shown that in our rats the inhibition of lactation due to adrenalectomy on the 4th day is in general not complete, though in one experiment the effects of adrenalectomy were so severe as to amount to complete inhibition. The lactational deficiency resulting from adrenalectomy could be restored to an extent varying between 60% and 100 % by administration of 3·0 mg. of deoxycorticosterone acetate daily. Earlier, Gaunt, Eversole & Kendall [1942] had reported that 17-hydroxy-11-dehydrocorticosterone (Kendall's compound E) and 11-dehydrocorticosterone (Kendall's compound A) were more effective than deoxycorticosterone acetate in maintaining lactation in adrenalectomized rats. Complete lactational replacement was afforded by compound E and by an extract of adrenal cortex while the response to deoxycorticosterone acetate, besides being less marked, appeared to be unrelated to the dose. Gaunt et al. thus concluded that for maintenance of