Accurate and credible data on the HIV epidemic are the cornerstone of the AIDS response. I am proud that UNAIDS leads the world’s most extensive data collection on HIV epidemiology, programme coverage and finance and publishes the most authoritative and up-to-date information on the HIV epidemic. UNAIDS’ data are the gold standard—no major report, speech or policy initiative on HIV is launched or made without referring to data collected and released by UNAIDS. UNAIDS has collected and published information on the state of the world’s HIV epidemic for the past 20 years. This information has shaped and guided the development of the response to HIV in regions, countries and cities worldwide. This edition of UNAIDS data contains the highlights of the very latest data on the world’s response to HIV, consolidating a small part of the huge volume of data collected, analysed and refined by UNAIDS over the years. The full data set of information for 1990 to 2015 is available on an interactive website: aidsinfo.unaids.org. In 2016, the world adopted the United Nations Political Declaration on Ending AIDS. This snapshot of the HIV epidemic shows us where we are in our commitment to end AIDS as a public health threat by 2030. It shows us how far we have come and how far we have to go.