The thirty-seven cases of osteosarcoma examined with computed tomography(CT) was evalu-ated. CT images were analyzed on the base of the intramedullary extension. cortical destruc-tion intralesional calcification extension to either the epiphysis or adjacent joint and soft tissue extension including muscular invasion and neuro-vasular invasion. And theses results were compared with the feature detected on plain radiographs. The assessment of the intra-medullay extension with CT was well established in the previous reports: in our series CT demonstrated the intamedullary extension 2.27 cm over the measurement of the lesion on plain radiograph and one skip metastasis on the distal femur in the patient with osteosarcoma on the proximal tibia. CT could depict the involvement of the epiphysis and joint however for the diagnosis and the assessment of either cortical destruction or intralesional calcification CT was not superior to plain radiographs significantly, CT provide valuable information about the soft tissue involvement specifically sparing of the neurovascular bundle(82%) However in the remaining 10 cases (28%) it did not differentiated the invasion of neurovascular bundle from the only close contact of mass to neurovascular bundle. CT proved to be a valuable method to assess the intraosseous and exteraosseos extent. particulary in planning limb salvage provedure.