In this study we have raised spontaneous Epstein-Barr virus (EBV)-positive lymphoblastoid cell lines (LCL) from the peripheral blood of human immunodeficiency virus (HIV)-infected individuals and of control patients with primary EBV infections. These LCLs were also raised in the presence of the viral inhibitor phosphonoformate (PFA); under these conditions, the in vitro infection of bystander B lymphocytes with EBV released in culture by in vivo infected B cells is inhibited. Thus, the latter LCLs are likely to represent the progeny of B cells latently infected by EBV in vivo. The LCLs raised in the presence or absence of PFA had the same phenotypic features, type of EBV latency, and growth pattern irrespective of whether they had been raised from HIV-seropositive individuals or patients with primary EBV infections or had been generated by infecting normal B cells in vitro. Studies on the production of inflammatory cytokines were conducted by Northern blotting or by determining the cytokine concentrations in the cell supernatants by immunoassays or bioassays. Three of eight LCLs from HIV-seropositive patients released TNF alpha and 5/5 released TNF beta, IL6 was present in the supernatants of 1/8 LCLs, and IL1 alpha and IL1 beta were not detected in any culture supernatant. No differences were noticed in the patterns of cytokine secretion among the LCLs from HIV-seropositive patients and in those raised from patients with primary EBV infections or obtained by infecting normal B cells in vitro with EBV. It is tempting to speculate that abnormally expanded EBV-harboring B cells in HIV-seropositive patients may participate in the pathogenesis of certain clinical manifestations by releasing inflammatory cytokines; some of these cytokines might also contribute to the in vivo spreading of HIV infection. However, the spontaneous LCLs from HIV-seropositive individuals do not display abnormal features compared to latently EBV-infected LCLs from other sources despite the high frequency of EBV-driven lymphoproliferative disorders observed in AIDS patients.