The AIDS Research Consortium of Atlanta (ARCA) is a nonprofit-making community-based clinical and epidemiologic research unit serving a population of more than 15,000 patients with HIV infection. This database derives from a core based on the Centers for Disease Control Adult Spectrum of Disease Study (ADS), of which ARCA is the oldest and largest site. The ARCA includes a variety of data distinct from the ADS database and was initiated in recognition of the need for a more local registry of patients to address therapeutic approaches and needs appropriate for the immediate community. Potential uses for this database include evaluation of the natural history of HIV, therapeutic efficacy, and drug safety.