The proposed factors that affect the prognosis of osteosarcoma are the patient's age, site and size of the primary lesion, pathologic features(type and grade), duration of symptoms, spread of disease (local or regional extension, distant metastasis) at diagnosis, the patient's sex, serum alkaline phos- phatase(ALP) and lactic dehydrogenase(LDH) levels, chromosomal number or DNA index, response to initial chemotherapy, location of the lesion on the bone, presence or absence of pathologic fracture, and mode of therapy. The purpose of this study is to analyze the factors that affect the 5-year survival rates of osteosarcoma. Total 25 patients were included in this study who had treated form Jan. 1988 to Apr. 1994. The overall 5-year survival rate of 25 patients was 65.43%, and the 5-year survival rates were sig- nificantly higher(P<0.1) in the groups in which limb salvage operation with neoadjuvant chemothera- py were performed(66.67%), with longer duration of symptoms(>2 months; 83.33%), with lower serum level of LDH(<300 U/L; 100%), and with smaller mass size(<10cm; 72.92%). However there were no significant differences in the 5-year survival rates according to age and sex of the patients. We also suggest that the better prognosis will be observed in the patients with the favorable radiologic response to the preoperative chemotherapy.