Although coverage rates and health outcomes are improving, many poor people around the world still do not benefit from essential health products. An estimated two-thirds of child deaths could be prevented with increased coverage of products such as vaccines, point-of-use water treatment, iron fortification, and insecticide-treated bednets. What limits the flow of products from the producer's laboratory bench to the end users, and what can be done about it? Recent empirical research suggests a crucial role for heavy subsidies.