Nine patients with osteosarcoma arising on the surfaces of long bones were evaluated restrospectively in the points of the clinical radiographic and histologic view. in reviewing the literature we classified the tumors into three subgroups: parosteal perio-steal and high grade surface osteosarcoma. Six patients had parosteal osteosarcoma two periosteal osteosarcomas and one high grade surface osteosarcoma. Radiographic and histologic findings can afford to the differentication of these tumor from each other and from classical osteosarcoma. All plain radiographs of four patients with parosteal osteosarcoma revealed heavily dense lobulated masses protruded from the adjacent long bones. CT could permitted the establi-shment of the extent of lesions whether either the marrows or the neurovascular bundles were involved or not in three parosteal osteosarcomas and one periosteal osteosacoma. In two periosteal osteosarcomas& one high-grade surface osteosarcoma either spotty ossific-ation or spiculated appearance of the tumor matrices were detected. Isotope bone scan gave the accurate informations not about the tumor extent but the metastases to bones. Histologically six parosteal osteosarcomas were generally low-grade but two of them shows high-grade in certain areas of the tumors. Two periosteal osteosarcomas contained particularly low grade chondroblastic componet. One high grade surface osteosarcoma was indistinguish-able from classical osteosarcoma. Authors believe that both radiographic and histologic findings could afford to the differentia-tion of these tumors from each from each other and from classical osteosarcoma and that one shoud pay attention to the surface osteosarcomas because of the variable tumor behaviors according to each subtype.