Alpha-1-antitrypsin (A-1-AT) and A-1-AT-elastase complex levels in cerebrospinal fluid have been evaluated in 11 children with viral meningitis (VM), 14 with bacterial meningitis (BM), 10 with tuberculous meningitis (TBM) and 10 investigated for, but found not to have meningitis (NM). A-1-AT concentrations in the NM group were lower than in the BM group (P = 0.0002) and the TBM group (P = 0.0005) but did not differ from the concentrations in VM; those in the VM group were lower than in the BM group (P = 0.0001) and the TBM group (P = 0.003) but no difference was found between the BM and TBM groups. A-1-AT-elastase complex concentrations in CSF were lower in the NM group than the BM group (P = 0.0001) or the TBM group (P = 0.0089), however those in the BM group were significantly higher than in the TBM group (P = 0.0001). A significant correlation existed in CSF between the protein concentrations and neutrophil counts as well as the A-1-AT and A-1-AT-elastase complex concentrations.