Pantohematogen stimulates hemopoiesis in mice with cyclophosphane induced bone marrow hypoplasia. The hemopoiesis recovery activated by pantohematogen is manifested by the granulocyte lineage hyperplasia in the bone marrow, rapid restoration of the polymorphonuclear leukocyte and monocyte counts in the peripheral blood, and the development of neutrophilia and monocytosis. The activation effect of pantohematogen on the bone marrow hemopoiesis is related to stimulating the precursor cell proliferation and differentiation and to increasing the functional activity of the hemopoietic microenvironment.