Meningitis remains a frightening disease with a high morbidity and mortality in spite of optimal treatment. In South Africa in particular, the incidence of HIV-infected patents with meningitis has risen considerably during the past decade. The first part of this meningitis study evaluated prognostic indicators in meningitis. In 100 adult patients with meningitis it was found that the Glasgow Coma Scale (GCS) at admission was a good indicator of the ultimate prognosis of the patient, with a GCS value of > 12 associated with a good outcome in 88% of patients. A GCS value of < 8 predicted an unfortunate outcome in 88% of patients. A high CSF protein level was also associated with an unfortunate outcome but the statistical significance was not as marked as with the GCS value. Age, CSF-neutrophil count, and glucose levels were also evaluated as possible prognostic indicators but were not found to be statistically significant. The electroencephalograms of 12 patients with pneumococcal meningitis showed that a grade 4 dysfunction within 48 hours of admission indicated a poor outcome; CT brain scans of 26 patients with TB meningitis showed that an adverse outcome was seen particularly in patients with TB meningitis and infarcts while in 33 patients with bacterial meningitis no specific sign was found to indicate a bad prognosis - probably due to the small number of patients evaluated. Prognostic factors in cryptococcal meningitis were lastly evaluated retrospectively in 44 patients; age, CSF white cell count and CD 4 counts were not found to be associated with outcome, while a GCS value of ≤ 14 at admission was found in almost three quarters of patients with an eventual adverse outcome. The second part of the study evaluated the impact of HIV-infection on meningitis. Between 1994 and 1998, the HIV-epidemic caused a marked shift in the spectrum of meningitis towards chronic infections such as TB and cryptococcal meningitis, while the incidence of HIV-related cases with meningitis rose from 14% in 1994 to 5% in 1998. A comparison of clinical, CSF and pathological findings and outcomes in 20 HIV-positive and 17 HIV-negative patients with tuberculous meningitis showed that HIV-infection does not significantly alter clinical and CSF findings in TB meningitis in South Africa, but ventricular dilatation and infarcts occur more frequently in HIV-positive patients. Diagnostic aids in meningitis were assessed in the final part of this study. The polymerase chain reaction for TB was measured in the CSF of 10 patients with suspected tuberculous meningitis and disappointingly only positive in two patients in spite of positive CSF cultures for TB in an additional four patients. Lymphnode biopsies were performed on seven patients with intracranial tuberculosis. Excision biopsy of an enlarged Iymphnode showing caseating granulomas and/or acid-fast bacilli confirmed the diagnosis of TB within 48 hours of admission. Thus, Iymphnode biopsies may be an effective and practical aid in diagnosing intracranial TB. Adenosine deaminase (ADA) levels are often elevated in both tuberculous and bacterial meningitis. ADA iso-enzymes analysis in 26 patients however, showed that the ADA2 iso-enzyme was the major contributor to increased ADA activity in the CSF of patients with tuberculous meningitis and not with bacterial meningitis. The EEG was evaluated as diagnostic aid in 55 patients with meningitis to discriminate between viral and non-viral meningitis. Sensitivities of 70% and 80% of VEEG and QEEG's respectively were attained for the prediction of patients with non-viral meningitis, while the VEEG had a specificity of 100% for the prediction of viral meningitis.