This study was designed to clarify the hormonal effect on the growth of osteoblast. And the osteoblasts from neonatal mouse were cultured in the medium at various concentrations of 17β-estradiol(EST), medroxyprogesterone acetate(MPA) in addition 10nM of dexamethasone(DMS) and alcohol for 48 hours. And in order to detect the response of osteoblast on the those hormones, the alkaline phosphatase(ALP) activity also was measured. 1. At 48 hours after culture of osteoblasts in media at various concentrations of hormones, EST has an effect on increasing of the cell number in fashion of dose dependent, whereas MPA did not increase the cell number. 2. Dexametasone significantly promoted differentiation of osteoblasts does dependently with increasing of ALP activity. 3. In osteoblasts culture in media supplemented with alcohol in the absence of 10nM DMS, EST increased significantly ALP activity, while decreased ALP activity of osteoblast in the presence of DMS, 4. In culture of osteoblasts treated with alcohol in the absence of 10nM DMS, MPA did not show any change of ALP activity. But in the presence of DMS, MPA decreased ALP activity of osteoblast. 5. EST plus MPA stimulated the ALP activity in osteoblasts treated with alcohol in the absence of DMS. While, in the cells treated with DMS, they synergistically decreased ALP activity.