Abstract. It has been reported that the fusion cells of dendritic cells (DCs) and tumor cells have anti-tumor effects. In this experiment, we examined the anti-tumor effects of fusion cells of bone marrow-derived DC type 1 (DC1) and irradiated tumor cells using a newly commercially available hemagglutinating virus of Japan-envelope (HVJ-E) after cell fusion, in a mouse model. To induce DC1, bone marrow cells (BMCs) from BALB/c mice were cultured with GM-CSF, IL-12 and IFN-Á. BMC-derived DC1 were fused with 20-Gy-irradiated Meth A cells (BALB/c-derived fibrosarcoma) using HVJ-E. We subcutaneously injected: i) the BMC-derived DC1, or ii) the fusion cells of the DC1 and the irradiated Meth A cells, into Meth A-bearing BALB/c mice. The injection of only DC1 showed a moderate anti-tumor effect, as we previously described. However, the fusion cells were more effective in not only suppressing tumor growth but also prolonging survival. These results suggest that the fusion cells of DC1 and the irradiated tumor cells using HVJ-E were more effective in tumor suppression than DC1 alone.