The Millennium Development Goals (MDG), which emerged from the United Nations Millennium Summit in 2000, are increasingly recognized as the over-arching development framework. As such, the MDG are increasingly guiding the policies of poor countries and aid agencies alike. This article reviews the challenges and opportunities for health presented by the MDG. The opportunities include that three of the eight MDG relate to health--a recognition that health is central to global agenda of reducing poverty, as well as an important measure of human well-being in its own right. A related point is that the MDG help to focus attention on those health conditions that disproportionally affect the poor (communicable disease, child health and maternal health), which should, in turn, help to strengthen the equity focus of health policies in low-income countries. Further, because the MDG are concrete, it is possible to calculate the cost of achieving them, which in turn strengthens the long-standing calls for higher levels of aid for health. The challenges include that, while the MDG focus on specific diseases and conditions, they cannot be achieved without strengthening health systems. Similarly, progress towards the MDG will require health to be prioritized within overall development and economic policies. In practice, this means applying a health 'lens' to processes such as civil-service reform, decentralization and the drawing-up of frameworks of national expenditure. Finally, the MDG cannot be met with the resources available in low-income countries. While the MDG framework has created pressure for donors to commit to higher levels of aid, the challenge remains to turn these commitments into action. Data are presented to show that, at current rates of progress, the health-related MDG will not be achieved. This disappointing trend could be reversed, however, if the various challenges outlined are met.