Objective To obtain plenty of pure osteoclasts for researching the function of osteoclasts in vitro.  Methods Osteoclasts were induced by bone marrow mononuclear phagocytes of mouse using medium with macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor-kappaB ligand (RANKL). The tartrate resistant acid phosphatase (TRAP) staining and bone resorption experiment were used to identify the osteoclasts.  Results The TRAP positive multinuclear cells were induced from mouse bone marrow mononuclear phagocytes after 3 days of inoculation

and plenty of resorption pits formed on bone slices after 7 days of inoculation. The number of TRAP positive multinuclear cells and bone resorption pits gradually increased during the period of induction.  Conclusion The osteoclasts were successfully induced from bone marrow mononuclear phagocytes in the presence of M-CSF and RANKL.