In sub-Saharan Africa, 43 million children under the age of 18 have lost one or both parents to AIDS, conflict or other causes. This large number strains systems by which families and communities have traditionally provided care for orphans. Support for some orphans is being provided by a variety of government, community and non-governmental organizations but this assistance reaches only a small percentage of those who need it. This paper estimates the funding required for necessary support to those most in need. We estimate that US$1-4 billion will be required annually by 2010, depending on whether support is provided to all orphans living below the poverty line or just those in most need. This is at least four times current funding and should be a priority topic for donor and national government resource allocation decisions this year.