Vaccine preparedness studies are necessary in order to prepare for launching preventive HIV vaccine efficacy trials. It is important to gather information on the risk of HIV infection among recruited populations, the extent and stability of HIV risk behaviors in these populations, and the risk of HIV infection associated with risk behaviors. This vaccine preparedness study is designed to expand the capacity of the HIVNET to implement HIV prevention trials, increase the diversity of its participant population, and further target populations at highest risk of HIV infection.