BACKGROUND: Osteosarcoma (OS) is an aggressive bone malignancy that primarily affects children and adolescents. Patients with metastatic disease at diagnosis have only a 20% survival rate. The poor survival rate of these patients is largely due to their lack of responsiveness to chemotherapy. However, the mechanisms underlying osteosarcoma chemoresistance remain unknown. MATERIALS AND METHODS: The effect of cisplatin, doxorubicin and etoposide was examined on OS cell lines. Affymetric Genechip analysis was used to examine differential gene expression. RESULTS: A correlation between increasing metastatic potential and increasing chemoresistance was observed in the MG-63 cell line and sub-line model. Microarray analysis of these cell lines revealed the differential expression of several genes potentially involved in chemoresistance including ABCG2, ADD3, NMT2, WNTSa and PTN. CONCLUSION: The identification of genes contributing to chemoresistance and determining the role these genes play is critical in characterizing patient responsiveness and overcoming chemoresistance in osteosarcoma patients.