In the past there was considerable evidence that cellular rather than antibody responses were more effective for tumor rejection (1 ). However, the task of identifying the tumor antigens recognized by T-cells was daunting technically. More recently there has been a growing optimism that the potential of tumor immunotherapy may at last be realized. This enthusiasm has been fed by a better understanding of the presentation and processing of peptides necessary for the induction of immune responses and the identification of new tumor targets. These developments will be discussed in this chapter. Because cancer vaccines are still in their infancy and largely experimental, detailed protocols for their production will not be presented.