Ulmus davidiana Planch (Ulmaceae) has long been known to have anti-inflammatory and protective effects on damaged tissue, inflammation and bone among other functions. To treat rheumatoid arthritis (RA), a herbal medicine, Ulmus davidiana Planch (Ulmaceae) extract (UD) is being used in traditional oriental medicine. The effect of UD on the proliferation and osteoblastic differentiation in non-transformed osteoblastic cells (MC3T3-E1) was studied. UD dose-dependently increased DNA synthesis (significant at 5-20 microg/ml). UD increased alkaline phosphatase (ALP) activity and prolyl hydroxylase activity of MC3T3-E1 cells (5-20 microg/ml). Antiestrogen tamoxifen eliminated the stimulation of proliferation and ALP activity of MC3T3-E1, which was induced by UD. UD at concentrations ranged from 30 to 100 microg/ml inhibited prostaglandin E2 production in MC3T3-E1. These results indicate that UD directly stimulates cell proliferation and differentiation of osteoblasts. These results also suggest and UD is effective for bone anti-resorptive action in bone cells.