The present study was performed to investigate the effect of $HTR^{(R)}$ (Hard Tissue Replacement) on osteogenesis in the mandibular bone defects. Eight adult male white rabbits weighing 2.5 to 3.0kg were used. Four bone defects (8mm in diameter and 4mm in depth) were made at the both mandibular body. In the control group, the right mesial bone defect was filled with blood clot and spontaneously healed. In the DFDB group, the right distal bone defect was filled with xenogenic demineralized freeze-dried bone. In the $HTR^{(R)}$ group, the left mesial bone defect was filled with $HTR^{(R)}$. In the $HTR^{(R)}-membrane$ group, the left distal bone defect was filled with $HTR^{(R)}$ and covered with BioMesh membrane. The rabbits were sacrified at 2,4,6 and 9 weeks after the operation and microscopic examination was performed. Results obtained were as follows: In the control and DFDB groups, inflammatory cells and the fibrous connective tissue existed and the bone growth was slower than $HTR^{(R)}$ group by 6 week, and there was intervention of the soft tissue at 9 week. In the $HTR^{(R)}$ group, bone trabeculi extended between the $HTR^{(R)}$ particles without intervention of inflammatory cells and the connective tissue at 4 and 6 weeks. In addition, extensive osseous ingrowth into the $HTR^{(R)}$ particles was observed at 9 week. Bone formation was more active in the $HTR^{(R)}$ group than the control and DFDB groups. There was not obvious difference in the bone healing rate between the $HTR^{(R)}$ and the $HTR^{(R)}-membrane$ group. These results suggest that the $HTR^{(R)}$ promotes osteogenesis in the bone defects and the $HTR^{(R)}$ group has no difference in comparison with the $HTR^{(R)}-BioMesh^{(R)}$ membrane group in bone healing.