The marginal budgeting for bottlenecks tool (MBB) is an analytical costing and budgeting tool that helps countries develop their health plans by taking into account the most effective interventions, cost and budget marginal allocations of their implementation to health services and assess their potential impact on health coverage, Health related Millennium Development Goals (MDGs) and health outcomes of the poor. It builds on the High Impact Interventions to reduce mortality as published in various scientific articles including The Lancet series on Child, Maternal and neonatal survival. The tool has been developed in the context of Highly Indebted Poor Country Initiative and Poverty Reduction Strategy Papers