Abstract: We report a typical case of multicentric synchronous osteosarcoma. An 8-year-old girl was referred to us. At diagnosis she had a dominant bone lesion in the left proximal tibia and other lesions in the pelvis, thoracic spine, right femoral shaft, and left lower limb, without any lung lesions. We administered high doses of cisplatin and doxorubicin hydrochloride, but they were not effective. A pulmonary metastatic lesion was first detected by chest X-ray 4 months after the diagnosis, and she died of pulmonary insufficiency within 1 year after the first presentation.