To investigate the effect of mouse marrow stromal cells on the growth of granulocyte—macrophage progenitor cells (CFU —GM) from mice with radiation injury. Semi—solid culture of CFU—GM on the confluent adherent stromal cell layers of marrow cells was adopted. The experimental data demonstrated that the numbers of nomal marrow CFU—MGM formed on stromal cell layers from mice with radiation injury were significantly reduced as compared with those from normal mice within 10d, especially at 3th and 5th day after injury. The supporting function of bone marrow stromal cells on the growth of CFU—GM was impaired under the irradiation conditions of which must not be neglected in clinical treatment of radiation—in,¬, duced hematopoiesis dysfunction.