The human immunodeficiency virus (HIV) commonly enters the central nervous system, disturbs brain function, and ultimately results in serious brain damage. The most serious manifestation of this infection of the brain is HIV-associated dementia, which includes severe memory loss, slowness in thinking, disorientation, and social incapacity. Most persons who are HIV infected do not develop severe dementia; however, perhaps 50% of those with AIDS and a smaller proportion of HIV-infected carriers suffer from more subtle brain disorders that can be revealed by proper neuropsychological testing. This book summarizes the current state of our knowledge about the neurocognitive disorders associated with HIV-1 infection. The book brings together contributions from leading authorities on the prevalence, qualitative features, natural course, and effects of neuropsychological impairments in persons with HIV infection. Neuropsychological data are related to findings from studies of brain imaging, neuropathology, and the effects of antiretroviral treatments.