Abstract
SUMMARY: Experiments are described which show that the in vitro synthesis of corticosterone under the influence of ACTH is inhibited by hydrocortisone, prednisolone and dexamethasone and that the relative potency of these three substances corresponds to their relative clinical anti-inflammatory activity. It is suggested that a direct adrenal inhibitory mechanism plays a physiological and pharmacological role, in addition to the regulatory mechanism controlling adrenal steroid function mediated by the pituitary.