Abstract: The present invention relates to the engineering of recombinant influenza viruses that express tumor-associated antigens. Expression of tumor-associated antigens by these viruses can be achieved by engineering specific epitopes into influenza virus proteins, or by engineering viral genes that encode a viral protein and the specific antigen as independent polypeptides. Tumor-bearing patients can be immunized with the recombinant influenza viruses alone, or in combination with another treatment, to induce an immune response that leads to tumor reduction. The recombinant viruses can also be used to vaccinate high risk tumor-free patients to prevent tumor formation in vivo.