Morpho-functional changes in mast cells in liver, intestinals, stomach, skin, adrenals, timus, bone marrow were studied in hypoxic hypoxia on outbred male rats. Systemic mast-cell's reactions in hypoxia manifestate themselves in migration and degranulation. Migration process from accumulating and mast-cell formation organs: namely from timus, bone marrow, into liver, intestines, stomach and adrenals are accompanied by the process of labrocytes in all the tissues under consideration but bone marrow at early stages of the experiment. Degranulation coefficient decreases and relationship between mast-cell of various forms undergoes rearrangement. We suppose, that mast-cell population in hypoxic hypoxia may participate in function regulation thanks to tissue blood-flow intensification, by its strengthening to biologically active substances in mast-cells.