In 1597 Francis Bacon stated that “knowledge itself is power” ¹ and Nelson Mandela, in the same vein, said in 2003 that “education is the most powerful weapon we can use to change the world”. ² In this issue of the Bulletin of the World Health Organization , Dermot Maher discusses the ethics of conducting population-based surveys involving clinical tests for research and surveillance purposes without routinely giving participants their test results, if these are positive, so that they can seek access to lifesaving treatment. Maher argues specifically that because antiretroviral treatment is now widely available, even in low- and middle-income countries, it is no longer ethical to fail to inform research participants when the result of a test for the detection of human immunodeficiency virus (HIV) infection turns out to be positive. ^{3 , 4}