The oncogene c-Jun has been found to be up-regulated in a variety of cancers including osteosarcoma. DNA enzymes (DNAzymes) are oligonucleotides capable of specific catalysis of target mRNA. A c-Jun DNAzyme inhibited the growth and metastasis of osteosarcoma in an orthotopic spontaneously metastasizing model of the disease. c-Jun down-regulation-mediated apoptosis in osteosarcoma cells involved caspase-1, caspase-2, and caspase-8, but not the Fas/FasL pathway. Clinically, knockdown of c-Jun with DNAzymes may proffer an improved treatment outcome for these tumors originating in bone.