To investigate in vivo reaction of newly developed glass ceramics, five milimeters of one proximal tibia of the rabbits were resected and the defect was replaced by ready-made glass ceramics cylinder of 5mm height. As a control, the other intact tibia was used in biomechanical study. Radiological examination was performed every 2 weeks postoperatively. Histological and electromicroscopic examinations were performed postoperatively at 2nd, 4th, 8th and 16th weeks. And fourpoint bending study was performed postoperatively at 8th and 16th week. Following findings were observed : On radiological examination, radiolucent line was seen around glass ceramic at 2-week X-ray. This line was obliterated gradually until 6-week X-ray. Remodelling of medullary cavity was noted from 6-week or 8-week X-ray, and was almost completed at 12-week X-ray. The glass ceramic was innocently incorporated into the host bone. On biomechanical examination, 8-week specimen was broken at 33% of break strength of control group and 16-week specimen was broken at 62%. On histological examination, in 2-weeks specimen, part of implanted glass ceramics was covered with new bone; in 4 weeks, implanted glass ceramics was surrounded by new bone and the surface was tightly bound to the new bone; in 8-week specimen, mature lamellated bone was showed and amount-of bone was increased. Based upon above findings, it was suggested that the glass ceramics was innocently incorporated into the host bone and revealed good biomechanical strength.