Timely, reliable and complete information on financial resources in the health sector is critical for sound policy making and planning, particularly in developing countries where resources are both scarce and unpredictable. Health resource tracking has a long history and has seen renewed interest more recently as pressure has mounted to improve accountability for the attainment of the health Millennium Development Goals. We review the methods used to track health resources and recent experiences of their application, with a view to identifying the major challenges that must be overcome if data availability and reliability are to improve.