This study was designed to evaluate of the effects ofB-estradiol, progesterone, dexamethasone, hydrocortisone, calcitriol and alfacalcidol on the cell proliferation and differentiation in the rat osteoblast-like osteosarcoma cells ROS 17/2.8. The proliferation of ROS 17/2.8 cell treated with 1 M B-estradiol, 1 M progesterone, 1 M hydrocortisone, 1 M dexamethasone, 10 (-8) M calcitriol and 10 (-8) M alfacalcidol was decreased by 19%, 56%, 60%, 64%, 28% and 38% of control, respetively. Production of TGF-Bl by ROS 17/2.8 cells treated with B-estradiol, progesterone, hydrocortisone, dexamethasone, calcitriol and alfacalcidol was elevated by 30%, 18%, 60%, 48%, 405% and 452% of control, respectively. Alkaline phosphatase activity of ROS 17/2.8 cell treated with hydrocortisone, dexamethasone, calcitriol and alfacalcidol was increased by 3.4 times, 12.9 times, 10.0 times and 5.1 times of control, respectively, but with B-estradiol and progesterone decreased by 39% and 10% of control respectively. Northern blot experiments demonstrated that calcitriol and alfacalcidol increased mRNA levels of both osteocalcin and osteopontin.