In 2010, randomized controlled trials (RCTs) of two different biomedical strategies to prevent HIV infection had positive findings. However, despite ongoing very high levels of HIV infection in some countries and population groups, it has been made clear by regulatory authorities that the evidence remains insufficient to support either product being made available outside of research contexts in the developing world for at least two years. In addition, prevention trials in endemic areas will continue to test new interventions against placebo. But the judgments of evidentiary standards are never value-neutral. Using the recent trials and their contexts as case studies, we examine the basis for these decisions, which will potentially delay access to scientific innovation to the people who are most urgently in need of it.