Dick Southwood was not only a renowned ecologist; he was also a shrewd politician who knew how to translate science into policy and practice. Under his influence, I have also followed a path from ecology through epidemiology to health policy at WHO. In this talk I will explain how WHO promotes and uses science to advance health globally, drawing on examples that include: publicizing the hazards of air pollution, creating laws to fight pandemics, eradicating polio, cutting market prices for essential medicines, protecting the Olympic Games from assault by Zika, and combining science and religion for the public good. While telling some stories of success, I shall not ignore the failures, admitting that WHO’s immense power has not always led to glory.