Abstract: Corydalis B has been reported to have strong analgesic and sedative actions resembling morphine and a number of tranquilizers. It is well.known that both morphine and the tranquilizers, such as reserpine and chlorpromazine, stimulate the release of ACTH, as well as depress the secretion of ACTH by the pituitary in response to a number of stressful stimuli under certain conditions. Since Corydalis B has been shown to have pharmacological properties similar to those of the aforementioned compounds, an attempt was made to study whether corydalis B would also affect the pituitary-adrenal axis. Experiments were carried out on male rats. A fall in adrenal ascorbic acid was used as the criterion for the release of ACTH. Subcutaneous injection of Corydalis B in a dose of 50 or 70mg/kg, the effective analgesic and sedative dosage, caused marked adrenal ascorbic acid and cholesterol depletion in intact rats. However, the ascorbic acid depleting effect of the compound disappeared in hypophysectomized rats. Pretreatment of rats with pentobarbital (40 mg/kg) or prednisolone (15 mg/kg) completely prevented the adrenal ascorbic acid depletion. Repeated injections of Corydalis B for 6 days, induced the development of tolerance to the pituitary-stimulating effect of the compound. From these results, it would appear that Corydalis B has a stimulatory action on the pituitary-adrenal system.