Objective To investgate whether the expression of osteoclast differentiation factor(ODF), intercellular adhesion molecule-1(ICAM-1) depended on the stage of osteoblastic differentiation from rat bone marrow mesenchymal stem cells(BM- SC).Methods BMSC (4 passage) were selected for osteogenic differentiation by treated with osteogenic supplements(OS). Cells were harvested by day 0, 3, 6, 9, 12, 18 respectively after osteogenic inducement. In each experiment, control and OS- treated cells were processed in parallel. ODF and ICAM-1 mRNAwere analyzed by semiquantitave RT-PCR assay.Results Expression of ODFwas enhanced with osteogenic differentiation guadully. whereas, expression of ICAM-1 was activated at OS- treated day 6, then keeping at a stable level.Conclusion This study indicated that BMSC undergoing osteogenic inducement was an ideal model for studying the differentiation and maturation of osteoblasts. During the early stage of differentiation along os- teoblasts from stem cells to osteocytes, BMSC or osteoprogenitor react somewhat differently from osteoblasts, suggesting the ability of osteoblasts to regulating differentiation and maturation of osteoclasts have been improved with osteogenic culture.