Among the secondary problems of patients with the human immune deficiency virus (HIV) infection are lymphadenopathy, atypical lymphoproliferations, and malignant transformations of lymphoid, muscle, and epithelial cells caused by infection with Epstein-Barr virus (EBV). The lymphoproliferative diseases associated with EBV infection include lymphocytic interstitial pneumonitis, lymphomas of primary and extra-nodal sites, such as the central nervous system (CNS), and mucosa-associated lymphoid tissue (MALT). EBV infection causes these diseases through a combination of mechanisms including use of virus-encoded transforming genes, stimulation of diverse cytokines, and interaction with receptors for the tumor necrosis factor (TNF) family of cytokines.