Based on the finding that cells producing antibodies to human immunodeficiency virus (HIV) circulate in the peripheral blood of HIV-infected individuals, attempts were made to immortalize such B cells with Epstein-Barr virus. Mononuclear cells from 58 HIV-seropositive subjects at various stages of HIV infection were transformed, and anti-HIV cell lines were derived from 4 subjects, all of whom were in early stages of infection. Seven of these cell lines have been stable with respect to antibody production for up to 15 months. Three lines are producing IgG antibody to the 41-kDa HIV transmembrane glycoprotein gp41 and 4 produce IgG antibodies to the 24-kDa HIV core protein p24, its precursors and a breakdown product. The antibodies are reactive by ELISA, by radioimmunoprecipitation, and by Western blot, demonstrating the feasibility of producing multiple stable cell lines synthesizing human monoclonal antibodies to HIV by immortalization of peripheral blood cells with Epstein-Barr virus.