The purpose of the Core is to recruit a cohort of at-risk and HIV+ older adult participants from 3 sources: HIV primary care clinics; HIV prevention and community based organizations that serve older adult populations; and, from the community. The Core will obtain complete, longitudinal assessments of cognitive and behavioral status for each participant, using standardized neuropsychological tests and psychosocial questionnaires. Biological specimens (including plasma, serum and DNA) are also obtained and stored for future testing of genetic polymorphisms that are related to drug metabolism, dementia and aging. The major functions of the Core are (1) to follow the cohort of older adult HIV+ persons who are enrolled in these studies through the transition to age 65; (2) to support the work of each project on which this Core is based, by maintaining a cohort that is sufficient in size and of sufficient duration; (3) to collect and store at no cost to each project participant information on clinical status and quality of life, as well as a DNA sample for future use; (4) to coordinate, analyze and disseminate all Core data. The Core will support the research projects of the Center by providing well-characterized, representative, demographically diverse, longitudinally followed samples of older adult HIV+ persons. The investigators in the Core will also ensure that the scientific goals of the Center are shared and will disseminate the data. The findings from these studies can then be applied in the development of interventions aimed at both maintaining the well-being of this vulnerable population and reducing HIV-related health disparities.