OBJECTIVE: To study the effect of simvastatin on the expression of bone morphogenetic protein-2 (BMP-2) and alkaline phosphates (ALP) activity in the primary cultured bone marrow stromal cells, and to elucidate the mechanism of the anabolic osteogenetic effect of simvastatin. METHODS: Bone marrow stromal cells in femur and tibia of adult mouse were cultured in vitro. after treated with different concentrations of simvastatin (0, 0.1, 0.2, 0.5 and 1.0 mumol/L) or recombinant human BMP-2 for 72 hours, ALP activity of bone marrow stromal cells was determined. BMP-2 expression of bone marrow stromal cells was analyzed by using immunocytochemistry and Western blotting. RESULTS: After treated with simvastatin for 72 hours, BMP-2 expression increased, while little BMP-2 expression could be observed in the control group. ALP activity also increased in a dose-dependent manner; t-test showed that ALP activity in the group which concentrations of simvastatin were 0.5 mumol/L (t = 2.35, P = 0.041), 1.0 mumol/L (t = 2.348, P = 0.041) had significant difference when compared with control group. CONCLUSION: Simvastatin lead to high expression of BMP-2 in bone marrow stromal cells, via the increased auto- or para-crine of BMP-2, and ALP activity increased. These may be parts of the mechanism on the anabolic osteogenetic effect of simvastatin.