Neurological complications of HIV infection cause considerable morbidity and are often associated with high mortality. These complications include not only the more common opportunistic diseases affecting the brain (cerebral toxoplasmosis, primary central nervous system lymphoma, progressive multifocal leucoencephalopathy, and cryptococcal meningitis) but also the AIDS dementia complex, with its characteristic cognitive and motor dysfunction, which is caused by HIV itself. Additionally, the peripheral nervous system is the target of several disorders, including a common painful neuropathy. Because these and other, less common, central and peripheral nervous system complications of HIV can often be specifically treated or effectively palliated, their accurate and timely diagnosis is important.