Despite significant efforts, the rate of new HIV infections worldwide remains 
unacceptably high, highlighting the need for new HIV prevention strategies. HIV 
pre-exposure prophylaxis (PrEP) is a new approach that involves the ongoing use 
of antiretroviral medications by HIV-negative individuals to reduce the risk of 
HIV infection. The use of daily tenofovir/emtricitabine as oral PrEP was found 
to be effective in multiple placebo-controlled clinical trials and approved by 
the United States Food and Drug Administration. In addition, the Centers for 
Disease Control and Prevention in the United States and the World Health 
Organization have both released guidelines recommending the offer of oral PrEP 
to high-risk populations. The scale-up of PrEP is underway, but several 
implementation questions remain unanswered. Demonstration projects and 
open-label extensions of placebo-controlled trials are ongoing and hope to 
contribute to our understanding of PrEP use and delivery outside the randomized 
controlled trial setting. Evidence is beginning to emerge from these open-label 
studies and will be critical for guiding PrEP scale-up. Outside of such studies, 
PrEP uptake has been slow and several client- and provider-related barriers are 
limiting uptake. Maximizing the public health impact of PrEP will require 
rollout to be combined with interventions to promote uptake, support adherence, 
and prevent increases in risk behavior. Additional PrEP strategies are currently 
under investigation in placebo-controlled clinical trials and may be available 
in the future.