Recent development of oral and maxillofacial surgery has taken an interest in the regeneration of facial bone defects. For the reconstruction of bony defects, autogenousbone grafts have been widely used. However, there are some clinical problems ; the morbidity of donor sites, resorption of autogenous bone graft and the availability of the proper form and size. The purpose of this study is to find the proper filling materials for the bone defects. The present study was designed to evaluate the roles and regenerating capacity of maikture of freeze-dried domineralized allogenic bone and hydroxylapatite. Fifteen adult New Zealand white rabbits were used as the experimental animal, Four trephine defects were made by drilling on the parietal bone of each rabbit. The size of each defects was 8x8mm. In first group, the defect was filled with freeze-dried demineralized allogenic bone and hydroxylapatite. The defect in second group was filled with autogenous bone chip only. The third group was filled with autogenous bone chip and hydroxylapatite. The fourth group was filled with freeze-dried dimineralized allogenic bone only. The results were carefully examined grossly and micorsocopically from the 2 weeks to 12 weeks postoperatively. The following results were obtained ; 1. In the case of the graft with autogenous bone chip only, new bone formation was more active than any other groups. 2. In the case of the graft with combination of freeze-dried demineralized allogenic bone and hydroxylapatite, new bone formation was similar to the case of autogenous bone and hydroxylapatite mixture. 3. In the case of the graft with freeze-dried demineralized bone, new bone formation was observed, but less than the other groups. And the time of new bone appeared was later than the other groups. A combination of freeze-dried deminearalized allogenic bone and hydroxylapatite plays an effective role in forming new bone. The results of this study may suggest the possible usage of the mixture of freeze-dried allogenic bone and hydroxylapatite as an alternative to autogenous bone in maxillofacial orthopedic surgery.