The Epstein-Barr virus (EBV), a B lymphotropic virus, is involved in a growing number of immunopathological disorders benign or malignant. The X-linked lymphoproliferative syndrome and its multifaceted clinical expression in a unique situation described in this issue by Purtilo. Among recent findings, the association between EBV and idiopathic interstitial pneumopathy (also named cryptogenic fibrosing alveolitis), is to be noted (6). From a molecular biology view-point, in vitro immortalization of B lymphocytes by EBV is under a pluri-genic (EBNA 2, EBNA 1, LYDMA) control. The role of EBV in oncogenesis appears different in Burkitt's Lymphoma (BL) and in nasopharyngeal carcinoma (NPC). In development of African BL, EBV appears to initiate the multistage carcinogenic event, through an early and massive infection. Other events include specific depression of T-cell immunity by hyperendemic malaria and c-myc onc-gene activation through chromosome translocation. In the genesis of NPC, the role of EBV still remain to be clarified although the strong and consistent association between EBV and the undifferentiated carcinoma of the nasopharyngeal (NPC) around the world favours an etiological relationship. The simple detection of IgA antibodies to VCA and EA allows early detection of the NPC, thus permitting a 95% cure rate at 5 years post-radiotherapy. Such an early diagnostic is of paramount public health importance. Furthermore, IgA/VCA and IgA/EA antibodies characterize precancerous conditions, giving the theoretical possibility of preventive interventions.