AIDS dementia complex (ADC) is a constellation of cognitive, motor, and behavioral dysfunctions frequently observed in persons with AIDS. Estimates of its prevalence vary. ADC may occur at any stage of AIDS but is usually associated with later stages of disease. Its severity varies among patients and often, but not always, is progressive. Various pathogenic mechanisms have been proposed for ADC, including effects of human immunodeficiency virus (HIV)-mediated cytokine production and direct neural cell damage by HIV. Antiretroviral therapy can delay or mitigate the symptoms of ADC.