Vaccination represents a success story in modern medicine and its principles have been found to be valid in different species, at least in the case of infectious diseases. As of today, there is little reason to believe that this would not be true in the case of tumours. It is now generally acknowledged that human tumours carry a mutational antigenic (non-self) repertoire of immunogenic potential that may be a suitable target for antitumour immune therapy. During the last years accumulating evidence from mouse experiments indicates that one can immunise prophylactically against cancers as effectively as against an infectious agent. However, in contrast to most experimental mouse tumour models, human tumours have in general been within their host for a long time and thus had the opportunity to influence their microenvironment and the larger immunological environment. Antigens capable of mediating specific rejection were found in human as well as in mouse tumours.