Experiments were conducted on Wistar rats, 160 to 180 g in weight. Epiphysectomy and pseudoepiphysectomy were carried out 14 days before the main experiment. Adrenal gland function was assessed by the rate of secretion of aldosterone and corticosterone into the adrenal vein and by the content of adrenaline in the adrenal glands. DOPA, dopamine and melatonine were administered into the third cerebral ventricle in a dose of 1 gamma per 100 g of weight, and intravenously in a dose of 100 gamma per 100 g of weight. Intraperitoneally melatonin was injected in a dose of 1 mg/100 g twice a day for 3 days. It was shown that administration of DOPA to males and of dopamine to females into the third ventricle of the brain increased the rate of aldosterone secretion in the intact rats. With different methods of administration melatonine decreased the rate of aldosterone and corticosterone secretion in the intact rats. Intravenous injection of melatonine to epiphysectomized rats stimulated the rate of secretion of the mentioned hormones.