The present study aimed to clarify the effect of simultaneous adding with supplements and BMP-2 on osteogenesis of osteoblasts. The proliferation and differentiation of human osteoblasts were evaluated on titanium plates with perforated holes that were laid beneath atelocollagen sponges impregnated with rhBMP-2, and adding the supplement (dexamethasone and β-glycerophsphate) to the culture medium. Simultaneous adding did not influence cell proliferation but increased slightly the ALP activity and osteocalcin content. However, the supplement was more effective than BMP-2 on cell differentiation. These results suggested that dexamethasone and β-glycerophsphate play an important role in the osteoblasts response to BMP-2.