Among cancers diagnosed worldwide on a yearly basis, 20% are thought to be associated with a viral infection. The viruses involved are, by order of decreasing incidence, the hepatitis viruses, the papillomaviruses and the Epstein-Barr virus. These virus-induced cancers generate a high level of interest not only for the study of mechanisms involved in the neoplastic transformation, but also for the set-up of specific immunotherapies including prophylactic and therapeutic antitumor vaccination.