In this brief review we describe the general principles of the antigenicity of human tumor cells, which can be recognized by T lymphocytes and particularly by cytolytic T lymphocytes. This antigenicity of tumor cells lead to the development of therapeutic anticancer vaccines that should induce tumor regressions or prevent the development of metastases in the vaccinated patients. We provide some information on a set of small scale clinical trials that we have carried out with metastatic melanoma patients, and which have provided encouraging though limited clinical results. Detailed immunological analyses with some of these vaccinated patients showed strong anti-tumor T cell responses and suggested that the main limiting factor for clinical efficacy is a phenomenon of resistance of the tumor to T lymphocyte attack. Current research projects aim at elucidating the mechanisms of this resistance and to develop new vaccination strategies that circumvent this roadblock.