Background: Timely reliable data on aid flows to maternal, newborn, and child health are essential for assessing the adequacy of current levels of funding, and to promote accountability among donors for attainment of the Millennium Development Goals (MDGs) for child and maternal health. We provide global estimates of official development assistance (ODA) to maternal, newborn, and child health in 2003 and 2004, drawing on data reported by high-income donor countries and aid agencies to the Organisation for Economic Development and Cooperation. Methods: ODA was tracked on a project-by-project basis to 150 developing countries. We applied a standard definition of maternal, newborn, and child health across donors, and included not only funds specific to these areas, but also integrated health funds and disease-specific funds allocated on a proportional distribution basis, using appropriate factors.