Considerable effort has been made to estimate the global resource requirements of scaling-up HIV/AIDS and tuberculosis (TB) interventions. There are currently several medium- and long-term global estimates available. Comprehensive country specific estimates are now urgently needed to ensure the successful scaling-up of these services. This paper reviews evidence on the global resource requirements of scaling-up HIV/AIDS and TB interventions. The purpose of this review is to summarise and critically appraise the methods used in the global estimates and to identify remaining knowledge gaps, particularly those relevant to country level estimation. This review found that the estimates of global resource requirements provide sound methodological guidance for countries on the basic steps to follow. However, there are still many areas that require further development or evidence. These include the following. Firstly, the methods used to assess the capacity to scale up HIV/AIDS and TB services need to be further refined. In particular countries need simple methods to assess human resource capacity. Secondly, investments need to be made to improve country level data on the costs and effectiveness of HIV/AIDS and TB services. In particular efforts should be focused on producing standardised unit costs for each intervention by country, which reflect the reality of domestic resource use. Thirdly, simple costing models, which appropriately integrate systems costs need to be developed for use at the country level. Finally, resources needs estimation needs to be embedded by countries in multi-sectoral expenditure planning processes. Countries and global agencies will continue to need estimates for different purposes at different times. Therefore attention should move away from specific estimates, to the longer term aim of building capacity at the country level, supported by global agencies. This will be of mutual benefit. Those making national resource estimates can learn from the experience of global estimation. Concurrently, global resource estimates can build on the evidence emerging from improved national resource estimates.