Abstract: Aim ：To observe the effects of sarsasapogenin(SAR) on osteoblasts and osteoclasts cultured in vitro. Methods ：Colonal murine calvarial osteoblast-like cell line MC3T3-E1 cells were cultured in vitro.MTT，p-nitropheneye phosphate and tinctorial method of alizarin Bordeaux were used to investigate the effects of SAR on the proliferation，ALP expression，and mineralization tuberculation of MC3T3-E1 cells.Mature osteoclasts were isolated from the long bone of one-day rat.Meanwhile，marrow cells of mouse bone were cultured with induction of 1，25(OH)₂VitD₃.During the culturing of osteoclasts or marrow cells，SAR of different concentrations was added into the medium.The number of osteoclasts was recognized as tartrate resistant acid phosphatase(TRAP)(+) multinucleate cells and the resorption lacuna on bone slice were examined with toluidine blue staining. Results ：Comparing with the control group，SAR （0.01，0.1，1 μg/mL） significanthy increased the proliferation of MC3T3-E1 cells (P<0.05，P<0.01).There was no significant difference in the expression of ALP in early proliferating MC3T3-E1 cells exposed to SAR of 0.01，0.1，1 μg/mL，but in the differentiation phase MC3T3-E1 cells，SAR improved ALP activity very significantly if compared with the control group，of which SAR of 1 μg/mL had the most promotion effect(P<0.01).In addition，compared to the control group，there were， to various extents，increased in the number of mineral nodes in MC3T3-E1 cells after 15day incubation with SAR of different conentrations.Furthermore，no obvious effects of 0.01-1 μg/mL SAR on mature osteoclast were observed.But typical osteoclasts were formed when marrow cells were cultured with the induction of 1，25(OH)₂D₃ in medium for 7 days while little or no osteoclasts were induced from marrow cells in the presence of SAR. Conclusion ：The results suggest that SAR can effectively promote the proliferation，differentiation and mineralization of osteoblasts cultured in vitro.Besides，SAR can inhibit the generation of osteoclasts from marrow cells.