Disorders of the nervous system frequently complicate Acquired Immune Deficiency Syndrome (AIDS). They may be related to the development of opportunistic agents (toxoplasmosis, cryptococcossis, cytomegalovirus, JC Virus), or primary CNS lymphoma. There is also a constellation of neurologic disorders which may result from direct Human Immunodeficiency Virus (HIV) replication in the CNS and HIV has been found in brain and CSF of numerous patients suffering from AIDS. The precise cellular localization of HIV is not known, but the macrophage seems to be a strong candidate for HIV replication in CNS.