Introduction: Limb salvage surgery has all but replaced amputation as the treatment of choice for sarcomas of the extremities. This dramatic change came about as the result of two important developments: effective chemotherapy and precision imaging techniques.In high-grade sarcomas the most significant predictors of survival are the location of the primary lesion, local control of the tumor, and the degree of necrosis in the primary tumor after intravenous neoadjuvant chemotherapy (histologic response).

Aim : To detect the response to preoperative chemotherapy and correlate with the biological characteristic of osteosarcoma

Materials and method:19 Patients wih primary osteo-sarcoma were studied (follow up 9 months to 7 years). Response to preoperative chemotherapy is made histologically according to the HUVOS staging system..Combination chemotherapy was used based on the Rosen T-10 protocol (high dose methotrexate) or the platine and adriamycine protocol.

Conclusions :The best response to preoperative chemotherapy was found in osteoblastic osteosarcomas (12% grade IV, 33% grade III, 33% grade II and 22% grade I tumor necrosis).Chondroplastic osteosarcomas showed less sensitivity to chemotherapy (o% grade IV, 40 % grade III, 20% grade II and 40% grade I tumor necrosis) and paraosteal and periosteal osteosarcomas were resistant to preoperarive chemotherapy.