The experiments performed on mature (4-6) and old (28-30 months) rats revealed changes developed in old animals in various links of regulatory system of aldosterone secretion: the decreased hypothalamohypophyseal control of mineralocorticoid secretion, increased sensitivity of glomerular zone to ACTH, vasopressin, K+ and of myocardium skeletal muscle and renal tissue to aldosterone. Changes in tissue sensitivity to aldosterone may be conditioned by the increased affinity of mineralocorticoid receptors to aldosterone in old age.