This study is conducted to investigate the use of induced osteoclastic cells by the intramuscular implantation of bone power as a short term in vivo model of bone resorption in sheep. The number of multinucleated cells and tartrate resistant acid phosphatase activity were gradually increased until 12 days after the implantation. Then the activity of enzyme did not significantly change. These results suggest that 12 day interval is enough to induce osteoclastic cells. Although the implantation of polyethylene also induced multinucleated cells, these cells seemed to possess slight activity of tartrate resistant acid phosphatase，which suggest that the enzyme activity can be used as a marker of osteoclastic cell actiyity in this model of bone resorption. The number of induced osteoclastic cells and the enzyme activity were not different between the first graft and the second one which was implanted 6 days later than the first implantatlon. It seems that overlapped and repeated implantations do not affect the induction and the actiyity of osteoclastic cells. The active vitaminD_3 stimulated the induction and the activity of osteoclastic cells，which showed that the differentiation of the osteoclastic cells responded to the endocrine factor. From these results，it is clear that the induction of osteoclastic cells is useful as a model of bone resorption in sheep．