Objective: To study the expression of osteosarcoma metastasis associated gene using a cDNA microarray, and screen new candidate genes related to the development, progress and osteosarcoma metastasis. Methods: Total RNA of a low metastatic osteosarcoma and a high metastatic osteosarcoma (M6 and M8 cell lines, respectively) was extracted, purified to mRNA and then reverse transcribed to cDNA. M6 was used as the experimental group and M8 as the control group, and the gene expression of cells from both of these two sublines was investigated using cDNA microarrays containig 8064 cDNA clones. The cDNA of M6 was labeled with cy3 and the cDNA of M8 was labeled with cy5. The two sublines were hybridized with the cDNA microarray. The hybridization signals were scanned with a Generation III array scanner and analyzed by Imagequant 5.0 software. Results: There were 330 differentially expressed genes between M6 and M8. In the M6 subline,152 genes were up-regulated and 178 genes were down-regulated compared to the M8 subline. These genes could be classified according to their function. Cell growth-related genes that were down-regulated included CCNG1, CDC2, APC10,and RPA3, while expression of the tumor suppressor genes, CDKN1A and CDKN2D, was up-regulated. Other genes that were differentially expressed included those that have been implicated in the regulation of signal transduction, metabolism and apoptosis. Conclusion: This study exploits a cDNA microarray approach to identifying genes that may be associated with metastasis. The gene expression profiles of osteosarcoma cell lines is a potentially important index in the search of new candidate genes related to tumor occurrence, development and metastasis.