The aim of this study was investigate the influence of the degree of damage suffered by MC3T3-E1 cells, which are osteoblast-like cells derived from the mouse, as compared to the degree of damage incurred by Balb c/3T3 cells. Immediately after loading, the amount of lactate dehydrogenase (LDH) increased in proportion to the load. In four days cultivation, no significant departure from the absorbance of the control group was observed other than in the 40g group, but in the MC3T3-E1 cells the amount of LDH was as great as that immediately after loading, whereas in the Balb c/3T3 cells the amount decreased to about 70%. A comparison of the two types of cells has revealed that the MC3T3-E1 cells, which take part in the bone formation, can withstand slightly less loading than the Balb c/3T3 cells.