This brief discusses important new opportunities to reverse the HIV epidemic in specific locations and among key populations at higher risk of HIV exposure. More and more countries are collecting and analysing data that enable these locations to be identified and addressed. Data collection is expanding, and new methods are being used to identify where localized epidemics may be emerging, where specific populations are the most affected by HIV and where vital HIV services are deficient or absent. These data are being combined in innovative ways, including with geographical information, to produce a more detailed and vivid understanding of the HIV epidemic, down to the district and subdistrict levels. This makes it possible to focus HIV programmes more precisely and effectively and to offer or adapt services to reach greater numbers of people in need.