The World Health Organization (WHO) recently published new global guidelines on how to do biobehavioral surveys related to HIV infection in a document known as the Blue Book. The Blue Book replaces the previous Red Book of guidelines for such surveys. The updated guidance keeps the global health community abreast of the evolving HIV epidemic, which has led to 37 million people currently living with HIV infection. Biobehavioral surveys provide population-level estimates for the burden of HIV disease and HIV-related risk factors, and they allow estimation of the coverage of prevention and treatment services for key populations that are at increased risk for HIV. Advances in available data and changes in the epidemic rendered the survey tools and guidelines in the Red Book out-of-date. In this blog post, we’re going to highlight how the new Blue Book addresses these critical gaps to deliver a manual better suited to the era of ending AIDS.