It has been demonstrated that alveolar macrophages (AM) are permissive for human immunodeficiency virus (HIV-1) after in vitro infection. However, data concerning in vivo infection of AM by HIV-1 still conflict. Therefore, we investigated AM collected by bronchoalveolar lavage from 15 HIV-1-infected patients. HIV-1 p24 and Gp120 antigens and viral RNA were not detected by immunocytochemistry and in situ hybridization, respectively, using 35S-labeled 3 kb Pol-Env, 0.350 kb Gag, and 0.150 kb U5 LTR cRNA probes. In contrast, when using polymerase chain reaction on DNA extracted from purified AM, HIV-1 DNA was detected in the seven patients tested. After short-term culture of alveolar cells from three HIV-1-infected patients and in vitro stimulation with granulocyte/macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor-alpha (TNF-alpha), HIV-1 replication was observed in most of the AM. These results demonstrate that AM are latently infected by HIV-1 in vivo but are not a site for viral replication. In contrast, HIV-1 replication occurs when AM are withdrawn from their local environment, enhanced by GM-CSF and TNF-alpha stimulation. This suggests either a negative control or an inadequate stimulation of HIV-1 replication in the alveolar environment.