We studied the role of beta-adrenergic mechanisms of regulation of erythropoiesis in the formation of the erythron system reaction during severe hypoxia. Blockade of beta-adrenoceptors after the incidence of hypoxic encephalopathy of different genesis was followed by an increase in the number of committed precursors in the bone marrow, hyperplasia of the erythroid hemopoietic stem, and rise in the count of peripheral blood erythrocytes. These changes were accompanied by decreased formation of abnormal erythrocytes.