The National Institute of Mental Health (NIMH), the National Institute on Aging (NIA), and the National Institute of Neurological Disorders and Stroke (NINDS) invite research grant applications focused on elucidating the mechanisms of HIV-associated neuropathogenesis in the context of aging, chronic infection with HIV, and long term exposure to Highly Active Antiretroviral Therapy (HAART). The neuropathogenic mechanisms of HIV-Associated Neurocognitive Disorders (HAND) may be distinct in the aging HIV-infected populations given the potential interactions between aging associated events, HIV-associated neurodegenerative processes, and exposure to HAART. Understanding the pathogenesis of HAND in HIV-infected individuals over 50 years of age, in light of potential interactions with HAART, neurodegenerative diseases, and aging-related co-morbid conditions are the focus of this announcement. Applications ranging from basic research to clinical diagnosis and treatment in domestic and international settings are of interest. Multidisciplinary research teams and collaborative alliances are encouraged, but not required.