[en] The regular pattern of radiation injury and its recovery in the bone marrow of rats was studied by scanning electron microscopy. Fifteen adult rats were irradiated with 625 rad of ⁶⁰Co γ-rays and the changes of femur marrow were observed 1, 3, and 7 days after irradiation. Twenty unirradiated rats served as controls. The results showed that the normal structure of marrow was distinctly destroyed 1 day after irradiation. Its main changes were dilatation and damage of the vascular sinuses and decrease of hemopoietic cells. The changes came to a climax on 3rd day, and the recovery began to take place after 7 days. The reticular cells and reticular fibres increased while hemopoietic cells significantly decreased, then they decreased gradually along with the restoration of hemopoietic cells. Fat cells appeared later. The foci of hemopoietic cells often appeared around the sinuses or small vessels and in the midst of fat cells. The interrelationship between hemopoietic parenchyma and stroma and the advantage of scanning electron microscopy are discussed