Abstract： Objective To investigate MRI manifestations of lumbar and proximal femoral bone marrow changes before and after recombinant human granulocyte colony stimulating factor (rhG-CSF) was subcutaneous injected for healthy adults. Methods Twenty healthy blood stem cell donors without hematologic disease were enrolled in this study. All of them underwent lumbar sagittal and proximal femur coronal MRI examination with spin echo T1 WI and fat-suppressed T2WI. The first examination were performed before subcutaneous injection of rhG-CSF for comparison. In 4-7 days and 30-60 days after injection, the other two examinations were performed. The signal changes of lumbar and proximal femoral bone marrow were investigated by reading pictures and calculating the contrasted noise ratio (CNR).Results Before rhG-CSF injection, all patients presented normal signal intensity of hone marrow. In 4-7 days after injection, all the 20 cases presented homogeneous signal decrease in lumbar vertebral bodys on T1 WI, accompanied by reduced fatty signal. In proximal femur, patchy or stripped hypointensity areas were found in intertrochanteric and subtrochanteric areas on T1 WI. On fat-suppressed T2 WI images, the signal of lumbar and proximal femoral bone marrow changed to equal or slightly-high signal intensity. In all cases,abnormal signal areas presented in lumbar and proximal femoral bone marrow occurred simultaneously in the same case. In the 10 cases received the third MRI during 30-60 days after rhG-CSF injection, signal intensity of lumbar bone marrow turned to normal in all sequence, but abnormal signal intensity areas were still existed and extended to distal part in femoral bone marrow, which appeared as symmetric stripped or patchy equal or slightly-low signal intensity on T1 WI and equal or slightly-high signal intensity on T2 WI. The CNR of lumbar bone marrow to subcutaneous fat before rhG-CSF injection, in 4-7 days and 30-60 days after rhG-CSF injection were 114. 11 ± 15. 11,71.04 ± 12. 25 and 91.64 ± 1 I. 68, respectively. Significant difference was found between before rhG-CSF injection and 4-7 days after injection ( P ＜ 0. 05 ) , but no significant difference between the others( P ＞ 0. 05 ). Conclusion After injection of rhG-CSF, the short-term changes of hematopoietic cells and fat content in bone marrow can be displayed on MRI, which provided non-invasive information for bone marrow transplantation.