Government spending on health from domestic sources is an important indicator of a government's commitment to the health of its people, and is essential for the sustainability of health programmes. We aimed to systematically analyse all data sources available for government spending on health in developing countries; describe trends in public financing of health; and test the extent to which they were related to changes in gross domestic product (GDP), government size, HIV prevalence, debt relief, and development assistance for health (DAH) to governmental and non-governmental sectors.