B-cell immortalization by Epstein-Barr virus (EBV) is dependent on permanent control of the cellular processes which normally regulate cell division and apoptosis, functions possessed by p53 in a number of normal cell types, In studies initiated to evaluate relationships between EBV latent genes and p53, p53 levels were found to increase approximately Ill-fold 4 to 5 days after EBV infection of purified resting human B cells; the induced p53 was transcriptionally active, Latent membrane protein 1 and, to a Lesser extent, EBV nuclear antigen 2 mediated the increase in p53 levels via activation of the NF-kappa B transcription factor.