The study of monocyte/macrophage functions after human immunodeficiency virus type 1 (HIV-1) infection may help in understanding the pathogenesis of AIDS. The production of four cytokines, tumor necrosis factor alpha (TNFα), interleukin-1β (IL-1β), interleukin-6 (IL-6), and granulocyte-macrophage colony-stimulating factor (GM-CSF), byperipheral bloodmonocytes/macrophages was evaluated after in vitro infection with HIV-l. HIV-1 infection ofthese monocytes/macrophages did not result in release of any of these cytokines. Similarly, treatment of uninfected cells with purified recombinant HIV-1 envelope protein did not result in cytokine production. After stimulation with endotoxin or endotoxin plus interferon-γ, HIV-1-infected monocytes/macrophages produced amounts of TNFα, IL-6, GM-CSF, and IL-1β comparable to that of uninfected cells. HIV-1 infection does not appear to induce or alter cytokine production bymononuclear phagocytes, which retain the capacity to produce these cytokines after endotoxin stimulation.