Over a period of six months, we have followed a total of six different EBV-transformed B cell lines, each of which has been infected by the human immunodeficiency virus (HIV-1). The results indicate that all of these lines were initially able to produce progeny HIV-1, but that over time three of them ceased to produce infectious virus and two lines failed to elaborate significant levels of reverse transcriptase activity into the medium. We further found that two of the latter cell lines continued to express the viral antigens p17, p24 and/or gp41, as determined by indirect immunofluorescence assay, at times after progeny HIV-1 could no longer be detected. Those cell lines which continued to secrete progeny HIV-1 did so intermittently with large amounts of virus production on some days but not others. We further found that treatment of such cells with 3' azido-3'-deoxythymidine (AZT) completely inhibited production of progeny HIV-1.