DNA vaccines against cancer have to activate an inadequate or damaged immune system in order to attack residual cancer cells. Although the potential problem of tolerance may be overcome by transplantation, provision of high levels of T-cell help is likely to be an important factor in stimulating effective immune pathways. The fusion gene approach appears to provide the required help, and offers a rational design for raising both antibody and T-cell mediated attack against lymphoma and myeloma, which express idiotypic antigen at the cell surface or as a secreted protein respectively. Intriguingly, preliminary data indicate that the fusion gene approach promotes antibody responses against a different cell surface tumour antigen, CEA. Strategies for using DNA vaccines to induce attack on processed peptides bound to MHC class I molecules are also being developed. We hope and anticipate that all categories of tumour antigen may be susceptible to this powerful new technology. The critical clinical requirement, however, will be to treat the presenting tumour with maintenance or restoration of immune capacity. We await results of the preliminary clinical trials with great interest.