BACKGROUND: There have been a few nationwide studies on the outcome of osteosarcoma. The KSPHO aimed to further elaborate on prognostic factors and survival for osteosarcoma over the study period (1989 to 2008). PATIENTS & METHODS: A retrospective analysis was performed on a KSPHO osteosarcoma survey data set of 290 patients that were registered from 20 institutions. RESULTS: There were 180 males (62.1%) and 110 females (37.9%) with an average age of 11.5 years (range, 1.835.7 years). Tumor locations were; distal femur (n=152, 52.4%), proximal tibia (n=59, 20.3%), proximal humerus (n=31, 10.7%), proximal fibula (n=11, 3.8%), axial bone (n=5, 1.7%) and elsewhere (n=31, 10.7%). Sixty patients (20.7%) presented with metastasis at the time of diagnosis and lung was the most frequently involved site. Histologic subtype was osteoblastic (n=185, 63.8%), chondroblastic (n=27, 9.3%), fibroblastic (n=3, 1.0%), others (n=29, 10.0%) and unknown (n=46, 15.9%). Chemotherapy regimens were cisplatin+doxorubicin (n=61), high dose methotrexate (HD MTX)+cisplatin+doxorubicin (n=126), HD MTX+ifosfamide+doxorubicin (n=17) and others (n=57). Surgery was performed in 247 patients and limb sparing was possible in 92.2% of the extremity cases. For the 180 cases whose histologic response to preoperative chemotherapy was available, there were 89 cases of good responders (49.4%). For 91 poor responders, postoperative chemotherapy was switched in 37 patients. With a median follow-up of 22.2 months (range, 0.1-234.4 months), the 5-year EFS was 55.3±3.8%. Presence of metastasis at the time of diagnosis, diagnosis in the period maximal growth rate, and tumor location at proximal humerus or proximal fibula tended to adversely influence the EFS. CONCLUSIONS: Prognostic factors identified in our study were similar to those described in previous studies. To maintain a high quality of treatment, it is necessary to develop a nationwide treatment protocol and our data could be used as a basis for that.