The dendritic cell (DC) is a potentially promising tool for cancer immunotherapy. To date, however, DC-based immunotherapy has not yielded data with which firm conclusions can be drawn. In the present study, we tested the dose-dependant enhancement of the anti-tumor effect induced by DCs. When large numbers of DCs were used, tumor growth was suppressed up to 41% when compared to control mice. Survival of the animals was prolonged to 54 days compared to the 33-day survival the control mice. The delayed-type hypersensitivity (DTH) response induced was 26-fold higher than in the controls. Larger numbers of DCs also led to higher expansion of IFN-gamma-secreting-CD8(+) T cells. Furthermore, the secretion of IL-12p70 and IFN-gamma by spleen cells were enhanced in proportion to the dosage. However, the level of IL-4 secreted from spleen cells was negligible compared to the level of IFN-gamma that was released. These results indicate that DCs induce Th1-dominant immune response and that more DCs could lead to better immunological results, a finding which was consistent with our therapeutic results.