Objective: To explore antitumor responses induced by recombinant vaccinia viruses expressing a p53 antigenic peptide (rVV-p53M) and enhanced effect of recombinant vaccinia viruses expressing costimulatory molecule B7 (rVVB7). Methods: A 135 Cys to Tyr point mutation p53-transduced P815 mastocytoma (P815-mp53) was used as an experimental tumor and the p53 protein as the model of tumor associated antigen． rVV-p53M and rVV-B7 were used as vaccine to test their induction of CTL and antitumor immunity. Results: Immunization of BABL/c mice with rVV-p53M could elicit specific CTLs, which could specifically lyse P815-mp53 cells. Immunization of mice with rVV-p53M could survive a part of mice challenged with 1×106 P815-mp53. Treatment with rVV-p53M could significantly prolong the survival oftumor-bearing mice. Admixture at 1:1 ratio of rVV-p53 M and rVV-B7 could enhance antitumor responses induced by rVV-p53M. Conclusion: Immunization with recombinant vaceinia virus expressing antigenic peptide is a useful alternative to peptide-based vaccine. Costimulatory molecule B7 can enhance antigenic peptide to induce antitumor responses.