Development Media International (DMI) is a London-based organisation which uses mass media campaigns to promote healthy behaviours in developing countries (www.developmentmedia.net). DMI has launched the world’s first scientific trial to examine how many lives can be saved using mass media alone. This major, 4-year project will take place in Burkina Faso, West Africa, in collaboration with the London School of Hygiene and Tropical Medicine (LSHTM). Our model predicts that we will prevent 20% of all child deaths. At the end of the project, the producer will know precisely how many lives they have saved.