In this trial of preexposure prophylaxis with tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) in men who have sex with men, TDF-FTC was found to be effective in preventing HIV-1 infection when it was taken before sexual activity. The prevention of infection with human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) remains a major public health challenge. 1 Owing to the lack of an effective HIV vaccine, consistent condom use remains the cornerstone of prevention, but biomedical interventions such as male circumcision and the use of antiretroviral drugs for the treatment of HIV infection represent additional prevention strategies. 2 – 5 Among the promising interventions is preexposure prophylaxis, in which antiretroviral drugs are started in HIV-negative persons before potential exposure to the virus. Daily oral preexposure prophylaxis with either tenofovir disoproxil fumarate (TDF) or the combination of TDF and . . .