Both animal models and studies in humans indicate that the immune response has enormous potential for the treatment of cancer, and that HLA plays a central role in this. This role is likely to become increasingly important in years to come, as effective strategies for immunotherapy of cancer are developed. In the last few years, much of the focus of tumour immunology has been on the identification and characterization of tumour-associated antigens that represent HLA-restricted tumour-specific targets. In the next few years the emphasis is likely to change, such that the HLA type and antigen profile of an individual's tumour may define the most appropriate form of therapy for the patient. The ability of tumour cells to down-regulate or lose expression of some or all HLA molecules may prove to be a major barrier to the effectiveness of such treatments. The next few years should show whether the potential of the advances in tumour immunology made over the last decade can be realized, or whether the application of these advances as therapeutic strategies falls short of their promise.