During a 2-year period, a total of 43 incident cases of central nervous system infections occurred in the adult (aged 15 years and above) population in Benghazi, Libya. This comprised 17 patients with aseptic meningitis, 10 acute bacterial meningitis, four tuberculous meningitis, five encephalitis, four neurosyphilis, two hydatidosis and one bilharzial myelopathy. The aetiology of the aseptic meningitis and encephalitis could not be established. The annual incidence rates of aseptic, septic and tuberculous meningitis, and encephalitis were 3.4, 2, 0.8 and 1 per 100,000 population, respectively.