Assessment of Pre-Exposure Prophylaxis (PrEP) Administered at Sexually Transmitted Disease (STD) Clinics

Inclusion Criteria: * Must be either a man who has sex with men or a transgender female * Male sex (at birth) * Willing and able to provide written informed consent * HIV-1 uninfected, defined as having a negative rapid HIV antibody test at both screening visit and enrollment and a negative 4th generation antibody/antigen test at screening * No laboratory evidence of a detectable HIV viral load (San Francisco site only) * Evidence of risk of acquiring HIV-1 infection including any one of the following: (1) Condomless anal sex with two or more male or transgender female sex partners during the last 12 months; or (2) two or more episodes of anal sex with at least one HIV-positive partner during the last 12 months; or (3) sex with a male or transgender female partner and any of the following STDs diagnosed during the last 12 months or at screening: syphilis, rectal gonorrhea, or rectal chlamydia. * Able to provide a street address of residence or phone number for themselves or two personal contacts who would know their whereabouts during the period of the demonstration project * Adequate renal function: creatinine clearance of 60 ml/min or greater as estimated by the Cockcroft-Gault equation within 45 days of enrollment * A urine dipstick with a negative or trace result for protein within 45 days of enrollment * Fluent in English or in Spanish Exclusion Criteria: * Signs or symptoms of acute HIV infection * Previously diagnosed active and serious infections including active tuberculosis infection or osteomyelitis and all infections requiring parenteral antibiotic therapy (other than STDs requiring intramuscular injections of antibiotics); active clinically significant medical problems including poorly controlled cardiac disease (e.g., symptoms of ischemia or congestive heart failure) or previously diagnosed malignancy expected to require further treatment * Hepatitis B surface antigen (HBsAg) positive * History of pathological bone fractures not related to trauma * Receiving ongoing therapy with any of the following: investigational antiretroviral agents (PEP is allowed as described in the protocol), interferon (alpha, beta, or gamma) or interleukin (e.g., IL-2) therapy, agents with significant nephrotoxic potential, other agents that may inhibit or compete for elimination via active renal tubular secretion (e.g., probenecid), and/or other investigational agents * Concomitant participation in a clinical trial using investigational agents, including placebo-controlled clinical trials using such agents * At enrollment, has any other condition that, based on the opinion of the investigator or designee, would preclude provision of informed consent; make participation in the project unsafe; complicate interpretation of outcome data; or otherwise interfere with achieving the project objectives