Hydrocortisone, prednisolone and dexamethasone clearly inhibited the reduction of skin histamine of albino rat with their optimal doses, individually not affecting the histamine content, when injected intramuscularly in divided doses 24 hours and 1 hour prior to an intraperitoneal injection of sinomenine hydrochloride 50 mg/kg. Their inhibitory effect reached the maximum, approximately 50 per cent inhibition, with the doses: 10 mg/kg of hydrocortisone acetate, 5 mg/kg of prednisolone acetate and 1 mg/kg of dexamethasone acetate respectively, whereas at the dosages larger than the above mentioned the inhibitory effect rather decreased. Relative potency of these glucocorticoids, in terms of doses producing the maximum inhibitory effect, was proportional to their anti-inflammatory effects. These results are reconfirmation of the earlier findings reported by Yamasaki and Yamamoto (Jap. J. Pharmacol. 13: 223, 1963), on the inhibitory effect of glucocorticoids on histamine release induced by dextran.