Periosteum in general is described as a specialized fibrous membrane of mesenchymal origin consisting of two basis layers : outer fibrous layer consists of irregularly arranged dense connective-tissue with fibroblasts, and inner osteogenic or cambial layer is composed of more loosely arranged fibers, greater vascularity and flatted spindle-shaped pre-osteoblasts. This periosteum may serve in controlling bone growth, especially mandibular growth has been emphasized. But, the periosteum enwrapping the facial skeleton have been studied for many years leaving a controversy in opinion regarding the function of these structures. We evaluated the bone formation activity of te periosteum in allogeneic bone grafts which bones are made of freeze-dried preparation preoperatively. We made the calvarial bone defects, 5 ${ imes}$ 7mm sized, amd grafted with allogeneic bone in rats, which a half of specimens has dissected the overlying periosteum and a rest intacted. After bone grafting, we evaluated the capacity ofbone formation of periosteum, 1, 2, 4, 6, 8 weeks postoperatively. There are subtle differences of bone formation during early healing period after demineralized allogeneic bone grafting between control groups with periosteum and experimental groups without periosteum.