We retrospectively reviewed 56 adults with culture-proven tuberculous meningitis (TBM), investigating clinical signs, cerebrospinal fluid (CSF) findings and outcome. There were 50 patients, aged 18-59 years, 39 with and 11 without human immunodeficiency virus (HIV) infection. Six were aged 60 years or older. Neurological signs of TBM in 18-59-year-olds were unaffected by HIV serostatus while, compared to those >or= to 60 years of age, there were more patients with meningism (86.0% vs. 33.3%; p=0.011) and fewer with seizures (12.0% vs. 50.0%; p=0.046). The HIV-infected 18-59-year-olds had significantly more extrameningeal tuberculosis compared to the non-HIV-infected (76.9% vs. 9.1%; p=0.0001) and 23.1% had 'breakthrough' TBM. CSF analysis revealed 12 patients (21.4%) with acellular fluid (more common in those >or= to 60 years of age, p=0.016), of whom three had completely normal CSF. A neutrophil predominance was found in 22 patients (39.3%). Only three patients (5.4%) had a positive CSF smear for acid-fast bacilli. In-hospital mortality occurred in 39 patients (69.1%), was similar in all study groups, and was not related to neurological stage. The diagnosis of TBM can be masked by lack of meningism in the elderly and by atypical CSF findings.