The author observed a case of osteogenic sarcoma in a 11-year-old female with complaint of painful swelling on face in right side. The observed results were as follows: 1. Large hematoma was obsered, and patient complanited painfull swelling on c/c site. 2. Predisposing factor of osteogenic sarcoma was not clear, but patient had history of extraction before patient visiting infirmary of our dental collage. 3. Serologic findings were not specific, and serum alkaline level was normal. 4. Radiographic findings were as follows: ① Diffuse faint radiopacity in the lesion ② Bony destruction and increased radiopaciy in right antrum ③ Displacement of multiple teeth on involved area(i. e ;＃12, 15. 55, 16, 17, 18), ④, Increased periodontal space in singel tooth(＃13) ⑤Destruction of bony crypt on involved teeth(＃13, 14, 15, 17, 18) ⑥ Loss of lamina dura of three teeth in involved area(＃11, 12, 16) 5. Computed tomographic findings were as follows: ① Large calcific and hetergenous component mass in the Rt. maxillary sinus, and this mass extending to Rt. maxilla, alveolar bone, ethmoid sinus. ②, Soft tissue bulging into Rt. side nasal cavity and oral cavity. ③ Bone destruction of maxillary sinus wall and Rt. alveolar bone.