Osteosarcoma includes several distinct varieties. It is therefore essential to rely upon a very specialized pathologist. It is necessary to stage the tumor and to histologically define the oncologic quality of the surgical removal (surgical margins). The limb salvage surgery in osteosarcoma involves several areas of risk: the biopsy, the extension of the tumor in the marrow spaces and canal, the impingement or plugging of the vessels by the tumor, the invasion of the joint tissues, the contamination of the joint space and/or soft tissue compartments. The reconstruction after bone segmental resection involves many problems, including long-lasting prostheses, bone bank, microsurgical techniques--the preoperative chemotherapy dramatically reduced the need for amputation, in favour of conservative surgery. A good response to chemotherapy (almost total necrosis of the tumor), is the most important factor correlated with a favorable prognosis. The more recent protocols aim to increase the tumor response and the survival rate through a very intense primary chemotherapy, using Adriamycin, high-dose Methotrexate, Cisplatin and Ifosfamide.