 This open-label, non-blinded, pharmacokinetic PK study will assess both tenofovir and emtricitabine components of Truvada concentrations within genital tract of male and females after a single dose of Truvada. Concentrations of the active drug will be measured in blood women and men, cervicovaginal aspirates and vaginal tissue women only, seminal fluid and rectal tissue men only. Samples will be obtained at 24 hours 1 day, 48 hours 2 days, 5 days, 7 days, 10 days, and 14 days post-dose. Each subject will undergo 2 biopsy days, at least 72 hours apart. Additionally, tissue samples will be evaluated ex-vivo for HIV infectivity. 