One of the adjunctive modes of diagnosing tuberculous meningitis (TBM) is to detect immune responses in the cerebrospinal fluid (CSF) to the Mycobacterium tuberculosis antigen. Up to 70% of clinical TBM reveal the presence of antimycobacterial antibody by the enzyme-linked immunosorbant assay. Defining the specificity of this immune response by Western blotting on separated M. tuberculosis antigen has been attempted in this study. Only antimycobacterial antibody-positive TBM cases were included in the study. An analysis of 30 such TBM cases showed a major immune reactivity to the 30- to 40-kDa region (93%) while a lower degree of immune reactivity was seen to the 14-kDa region (87%) and to the 18- to 25-kDa region (60%). Grossly the antibody reactivity on Western blot correlated with the ELISA results. Assessment of antimycobacterial antibody in the neurologic control CSF samples of pyogenic meningitis [n = 10], cryptococcal meningitis [6], neurocysticercosis [28], neurosyphilis [8], viral meningoencephalitis [8], carcinomatous meningitis [8], iatrogenic meningitis [6], and nonneurological control CSF samples from patients undergoing spinal anesthesia [20] revealed the presence of antibody in the CSF of 2 of the 10 pyogenic meningitis and 5 of the 28 neurocysticercosis cases. A Western blot analysis of these 7 cases revealed immune reactivity to 30- to 40-kDa regions only in 2 cases (1 of pyogenic and 1 of neurocysticercosis). The remaining 5 CSF samples did not reveal any immune reactivity on Western blotting, although ELISA demonstrated antimycobacterial antibodies. The antibody response to M. tuberculosis lipoarabinomannan and 38-kDa antigen by ELISA revealed 70.58 and 41.17% positivity, respectively. Thus this study has demonstrated that, by Western blotting, the major immune response is to the 30- to 40-kDa region, namely, lipoarabinomannan. Further, this finding will be useful for specific immunodiagnosis of the TBM.