AbstractThe implantation of combined hydroxyapatite (HAP) and autogenous red bone marrow (BM) was used to repair bone defect resulting from fibrodysplasia of bone in one case. After one year, the specimen was studied under optical and electronic scanning microscopes in order to study the biological features, histological changes and osteogenesis of hydroxyapatite implanted in the body. The results showed that there was not any inflammatory, toxic, or immune reaction in the tissue surrounding HAP-BM, and that HAP implanted was almost completely replaced by newly formed bone, and was firmly united to the surrounding bony tissue. This indicated that in the body HAP had a good biocompatibility and that HAP-BM provided the scaffold for osseous ingrowth as wellas boneinduction substances. The whole result was to that of the autogenous bone graft.