The human immunodeficiency virus (HIV), the etiological agent of acquired immunodeficiency syndrome (AIDS), directly affects the central nervous system (CNS) and often causes cognitive, motor, and behavioral changes and eventually a dementia prior to death. Suggestive evidence for the early onset of HIV-induced mental changes is derived from numerous case reports, the nature of subcortical CNS postmortem findings, and early abnormalities seen in cerebrospinal fluid, on brain computed tomography, magnetic resonance imaging, and electroencephalography, and on neuropsychological tests administered to patients with AIDS and AIDS-related complex. However, whether clinically significant cerebral impairment can precede symptoms of immunosuppression is unclear. A few studies have shown poorer performance on neuropsychological tests by asymptomatic HIV-infected subjects compared with uninfected controls, but several studies have not found this difference. To address this controversy, the current literature is reviewed, methodological problems are discussed, and recommendations are made for evaluation and treatment when early HIV-induced mental changes are suspected.