This study is designed to prepare for the implementation of a second study, HPTN 035: A Phase II/III Safety and Effectiveness Study of the Vaginal Microbicides BufferGel and PRO 2000/5 Gel (P) for the Prevention of HIV Infection in Women. HPTN 035 requires an average HIV seroincidence rate of 5-6 percent among enrolled participants. The primary objective of the present study is to estimate the rates of HIV seroincidence among women targeted for inclusion in HPTN 035.