Objective: To determine whether bone marrow mesenchymal stem cells (BM-MSCs) are presented in the different fractions of bone marrow cells and whether the efficiency of colony forming unit-fibroblastic(CFU-f) formed by BM-MSCs is regulated by 1,25(OH)2D3 and prostaglandin E2(PGE2). Methods:Total bone marrow cells or non-adherent bone marrow cells derived from total bone marrow cell cultures for 1 day were separated into the mononuclear cell fraction and the granulocyte/erythrocyte fraction or the mononuclear cell fraction, the granulocyte fraction and the erythrocyte fraction by density-gradient centrifugation and were cultured in the absence or presence of 10-8mol/L 1,25(OH)2D3 or 10-7 mol/L PGE2 for 10 days. The resulting cells were stained with methylene blue and the number of CFU-f was counted. Results:①The CFU-f formed by mononuclear cell fraction accounted for about 10% of the total CFU-f, and CFU-f formed by granulocyte/erythrocyte fraction, granulocyte fraction and erythrocyte fraction accounted for about 90%,47% and 35% of the total CFU-f, respectively; ②The fractions derived from the non-adherent bone marrow cells accounted for about 71% of the total CFU-f, which was more than those formed by the fractions derived from total bone marrow cells; ③ Treatment of 1,25 (OH)2D3 and PGE2 enhanced the CFU-f formation of the mononuclear fraction and the granulocyte fraction derived from total bone marrow cells and the mononuclear cell fraction, the granulocyte fraction and the erythrocyte fraction derived from non-adherent bone marrow cells. Conclusion: Our results indicate that BM-MSCs are presented in the different fractions of bone marrow cells,and 1,25(OH)2D3 and PGE2 play a role in stimulating proliferation of BM-MSCs.