Intravenous injections of bradykinin, cellulose sulphate (a kinin-releasing agent) or adrenaline cause rapid leucocytosis in the rat. The effect of the two former drugs is abolished by adrenalectomy, that of the latter is unaffected by this treatment. Bradykinin and agents capable of releasing it in plasma, may induce leucocytosis via adrenaline released from the adrenal gland.