MMP-9 or Gelatinase B, a member of the matrix metalloproteinase family (MMPs), plays important roles in physiological events such as tissue remodeling and in pathological processes that lead to destructive bone diseases, including osteoarthritis and periodontitis. In addition to its effect on the increase of total bone mass, statin (an HMG-CoA reductase inhibitor) suppresses the expression of MMPs. In this study, we proposed that simvastatin reduces MMP-9 expression in osteoblasts and HT1080 fibrosarcoma cell line. Gelatin zymography, Western blot analysis and reverse transcriptase-PCR were used to investigate the effects of simvastatin on MMP-9 in primary calvaria cells, U2-OS osteosarcoma cells, and HT1080 fibrosarcoma cells. The results from gelatin zymography and Western blot analysis revealed that simvastatin suppressed MMP-9 activity in these cells in concentration- and time-dependent manners. The effective concentrations of simvastatin were 100 - 500 nM, 5 - 15 microM, and 2.5 - 10 microM in primary calvaria, U2-OS, and HT1080 cells, respectively. Collectively, these results suggest that simvastatin is a potent drug for inhibition of MMP-9 expression in osteoblastic cells and HT1080 fibrosarcoma cells.