Abstract: The potential application of dendritic cells (DC) sensitized with cytosine-phosphoric acid-guanine (CpG) oligodeoxynucleotide (ODN) and tumor antigen as a vaccine against murine melanoma was investigated with freshly isolated mouse bone marrow-derived dendritic cells. For the DC vaccine preparation, DC were sensitized with the B16 tumor antigen and CpG ODN was used to promote further maturation of the DC. The immunogenic activity of the vaccine was evaluated in vitro by determining the proliferation of T lymphocytes and the killing effect of cytotoxic T lymphocytes (CTL) on B16 tumor cells. The DC vaccine was injected intraperitoneally and tumor inhibition in mice bearing B16 xenografts was examined. All mice were cared for under an approved SIMM Institutional Animal Care and Use Committee (IACUC) protocol. In vitro, this DC vaccine promoted the proliferation of T lymphocytes and showed a potent killing effect on the target B16 cells. In vivo experiments showed that after treatment or pre-immunization both the tumor volume and weight were significantly decreased. The DC vaccine with CpG ODN and tumor antigen exhibited an inhibitory effect against melanoma, providing a potential method for melanoma cancer treatment.