Purpose : We performed the present study to investigate whether osteotropic hormomes play roles on the nitric oxide (NO) production in culture of ROS 17/12.8 osteoblastic cells. Materials and Methods : The osteoblastic cell line ROS17/2.8 cells were cultured In F12 medium supplemented with $5\%$ fetal bovine serum (FBS) at $37^{circ}C$ in a humidified atmosphere of $5\%;CO_2$ in air. ROS17/2.8 cells were plated in 96-well plates at a density of $2-3 imes10^3cells/well$ and grown to confluence. Then the cells were pretreated with osteotropic hormones (parathyroid hormone (PTH) 20-500 ng/mL, 1, 25-dihydroxycholecalciferol $(1,;25[OH]_2D_3)$ 1-100 nM; prostaglandin $E_2 (PGE_2)$ 20-500 ng/mL in the medium supplemented with $0.4\%$ FBS for 72 hours and the cells were treated with cytokines $(TNF{alpha};and;IFN{gamma})$ in phenol red-free F12 medium for an additional 48 hours. NO synthesis was assessed by measuring the nitrite anion concentration, the reaction product of NO, in the cell culture medium using Griess reagent. Results : PTH and $1,;25[OH]_2D_3$ pretreatment induced a significant increase in NO production in the presence of $TNF{alpha};and;IFN{gamma}.;PGE_2$ slightly induced NO production compared to the control group. But, $PGE_2$ pretreatment did not affect in NO production in the presence of $TNF{alpha};and;IFN{gamma}$. Conclusions : These results suggest that the actions of osteotropic hormones In bone metabolism may be partially mediated by NO in the presence of cytokines.