Osteoclasts resorb bone by the hydrogen ions and proteolytic enzymes in the localize environment under the ruffled border. Before releasing hydrogen ion and enzymes, osteoclast should attach to bone surface very tightly and make a room to release enzymes and hydrogen ion in the center. Specialized attachment molecule in the cell membrane, such as integrin, is associated with specific noncollagenous protein in the matrix, which has specific amino acid sequence (Arginine-Glycine- Aspartic acid sequence). We may speculate that osteoclast action would be decreased if the integrin is blocked by antibody or RGD protein. In this study, the osteoclasts were cultured on the coverslip or bone slice with or without RGD protein in the culture medium, and numbers of growing giant cells were much less in group with RGD protein. The number resorption pits, formed on mineralized bone slice, was also lower in the group adding RGD protein in the medium. And we made a conclusion that the osteoclastic bone resorption was inhibited by soluble RGD protein.