The HIV pandemic continues to be one of our greatest contemporary public health threats. Policy makers in many middle- and low-income countries are in the process of scaling up HIV prevention, treatment and care services in the context of a reduction in international HIV funding due to the global economic downturn. In order to scale up services that are sustainable in the long term, policy makers and implementers need to have access to robust and contemporary strategic information, including financial information on expenditure and cost, in order to be able to plan, implement, monitor and evaluate HIV services. A major problem in middle- and low-income countries continues to be a lack of basic information on the use of services, their cost, outcome and impact, while those few costing studies that have been performed were often not done in a standardized fashion. Some researchers handle this by transposing information from one country to another, developing mathematical or statistical models that rest on assumptions or information that may not be applicable, or using top-down costing methods that only provide global financial costs rather than using bottom-up ingredients-based costing. While these methods provide answers in the short term, countries should develop systematic data collection systems to store, transfer and produce robust and contemporary strategic financial information for stakeholders at local, sub-national and national levels. National aggregated information should act as the main source of financial data for international donors, agencies or other organizations involved with the global HIV response. This paper describes the financial information required by policy makers and other stakeholders to enable them to make evidence-informed decisions and reviews the quantity and quality of the financial information available, as indicated by cost studies published between 1981 and 2008. Among the lessons learned from reviewing these studies, a need was identified for providing countries with practical guidance to produce reliable and standardized costing data to monitor performance, as countries want to improve programmes and services, and have to demonstrate an efficient use of resources. Finally, the issues raised in this paper relate to the provision of all areas of healthcare in countries and it is going to be increasingly important to leverage the lessons learned from the HIV experience and use resources more effectively and efficiently to improve health systems in general.