Rationale: The risk of developing active tuberculosis in persons with latent Mycobacterium tuberculosis infection is substantially increased shortly after HIV-1 seroconversion. Immune responses in the lung are important to restrict the growth of Mycobacterium tuberculosis to prevent the development of disease. Objectives: To investigate innate and adaptive immune responses to Mycobacterium tuberculosis in bronchoalveolar lavage from HIV-1 infected persons without active tuberculosis. Methods: Peripheral blood was drawn and bronchoalveolar lavage performed on healthy, HIV-1 uninfected (n=21) and HIV-1 infected (n=15) adults. Growth of Mycobacterium tuberculosis was assessed in monocytes and alveolar macrophages. Cytokine expression by mycobacteria-specific CD4 and CD8 T cells was measured by intracellular cytokine staining or IFN- ELISpot. Measurements and Main Results: Mycobacterial growth in monocytes or alveolar macrophages from HIV-1 infected and uninfected persons did not differ. Total CD4 T cell frequencies in bronchoalveolar lavage were lower in HIV-1 infected than in HIV-1-uninfected persons (p<0.001). Mycobacteria (BCG)-specific CD4 T cell responses in bronchoalveolar lavage were severely impaired: Frequencies of cells expressing IFN- or, TNF-, as well as polyfunctional cells, expressing IFN-, TNF- and IL-2 together, were lower in HIV-1 infected persons than in uninfected controls (p<0.01 for all). Conclusions: In addition to a total CD4 T cell deficit, the function of mycobacteria-specific CD4 T cells is significantly impaired in the lung of HIV-1 infected persons, which may account for the HIV-1-associated elevated risk for developing tuberculosis.