Lymphocytic alveolitis in HIV-infected patients probably represents a local immune response to HIV-infected cells in the lung. The intensity of lymphocytic alveolitis may therefore reflect the viral load in the lung. If so, treatment that reduces viral load in the lung (e.g., HAART) should also decrease the number of cytotoxic T lymphocytes (CTLs) in the alveolar space and should return pulmonary immune responses toward normal.