It is the aim of this study to investigate the effects of sodium fluoride and sodium orthovanadate upon the proliferation and activity of the osteoblast (MC3T3-E1 cells). MC3T3-E1 cells were cultured in α-MEM containing 10% FBS and various concentration of sodium fluoride and sodium orthovanadate was appended to serum free media. DNA synthesis was examined through the [^³H] thymidine incorporation into DNA. Collagen synthesis was examined through the [^³H] proline incorporation into collagenase digestible protein and noncollagen protein. The following results were drawn; 1. Sodium fluoride stimulated the DNA synthesis of osteoblast significantly in dose-dependent manner within the concentration from 2µM to 10µM (P<0.005). 2. Sodium orthovanadate stimulated the DNA synthesis of osteoblast significantly in dosedependent manner within the concentration from 2µM to 8µM, however showed diminution at 10µM (P<0.001). 3. Sodium fluoride and sodium orthovanadate stimulated the percent collagen synthesis of osteoblast significantly in dose-dependent manner within the concentration from 5µM to 10µM (P<0.001). 4. Sodium fluoride and sodium orthovanadate stimulated the non collagen synthesis of osteoblast significantly in dose-dependent manner within the concentration from 5µM to 10µM (P<0.001). In conclusion, sodium fluoride and sodium orthovanadate stimulate the proliferation and activity of osteoblast by stimulation of DNA synthesis and collagen and noncollagen synthesis in osteoblast.