Clinical symptoms of the central and peripheral nervous system occur in about 40% of patients wit HIV infection. At autopsy, CNS lesions can be demonstrated in even higher percentages. Primary sequelae of HIV infection--either due to direct viral effects or the immunopathologic response of the human host--are acute aseptic meningitis or mengingo-encephalitis, HIV encephalopathy, myelopathy, neuropathy, and myositis. Secondary consequences of immunodeficiency in AIDS are opportunistic infections with other viruses, bacteria, fungi, and protozoa, e.g. CMV, HSV and HZV encephalitis, mycobacterial CNS infections, neurosyphilis, cryptococcal meningitis, and last but not least cerebral toxoplasmosis. The main secondary malignoma of the CNS is lymphoma. Together these disorders form a complex spectrum of central and peripheral neurological symptoms.