Epstein-Barr virus (EBV) infection is associated with infectious mononucleosis (IM) and with a number of human malignancies including nasopharyngeal carcinoma (NPC), Hodgkin's disease (HD) and immunoblastic lymphoma (IL). Their potential for immunotherapeutic treatment by cytotoxic T cells (CTL) is dependent on the degree of EBV antigen expression, with the best prospect revolving around IM where a vaccine is under development and IL of transplant patients where adoptive transfer of in vitro reactivated CTL has already been demonstrated to be effective. The opportunities for effective immunotherapy in the treatment of NPC is reduced since the available targets are limited to relatively non-immunogenic proteins. Perhaps more importantly, the development of immunotherapeutics is not considered a realistic commercial proposition. The best chance of developing an effective vaccine is to exploit the similarities in phenotype between HD and NPC since a vaccine to the former is likely to have more commercial appeal.