MRI is now the method of choice for bone marrow imaging. The MR appearance of bone marrow is influenced by the relative amounts of its fatty or hematopoietic components. In the following study, we report different patterns in changes consistent with reconversion into hematopoietic tissue of fatty marrow that were observed in 3 patients who received hematopoietic growth factors in combination with their chemotherapy for musculo-skeletal tumors of lower limbs.