Responses to mycobacterial and nonmycobacterial antigens were examined in bronchoalveolar cells (BAC) and peripheral blood mononuclear cells (PBMC) from patients with active pulmonary tuberculosis (n = 16) and healthy subjects (n = 23). DNA synthesis in BAC (but not PBMC) from tuberculosis patients was significantly increased in response to the mycobacterial antigens purified protein derivative (PPD), antigen 85, and mannose-capped lipoarabinomannan but not to nonmycobacterial antigens. The response to PPD was also increased in enriched alveolar lymphocytes from tuberculosis patients (P < .05). The frequency of interferon-γ but not interleukin-4- or -10-producing cells by ELISAspot was increased in PPD-stimulated BAC from patients with tuberculosis (P < .05). Accessory function of alveolar macrophages for T lymphocyte responses was similar and suppressive activity was variably decreased in tuberculosis patients. Thus, there is compartmentalization of mycobacterial antigen-specific lymphocytes to the lungs during active tuberculosis that on challenge produce a Th1-type cytokine host response.