Objective: We have studied the vaccine and synergic effects of IL-12 and B7-1 transfectant on antitumor immunity in vivo. Methods: The retrovirus vector encoding mIL-12 and mB7-1 gene was tranfected into EL-4 thymic lymphoma cells respectively. The cells were used to treated as the tumor vaccine and the therapeutic effect was observed. Results: In contrast to the mice immunized with EL-4/Wt or EL-4/Neo groups, the tumorigenicity of EL-4/IL-12 transfectant was decreased (p<0. 001). The EL-4/IL-12 and EL-4/B7-1 cells irradiated with 60Co showed significant systematic protective effects against the sequence rechallenge of EL-4/Wt. EL-4/IL-12 cells with 60Co irradiated delayed the occurrence of tumor and prolonged the survival period of tumor bearing mice. Combination of the vaccines of EL-4/IL-12 and EL-4/B7-1 result in the enhanced the therapeutic effect compaired with each single transfectant group (p<0. 001). Conclusion: The results showed that IL-12 transduced cells could enhance the antitumor immunity of host as cancer vaccine. Combination of the EL-4/IL-12 and EL-4/B7-1 transfectant could improve immunity of host and is a prospect Cancer vaccine.