Health sector reform is underway or under consideration.in countries throughout the world and at all levels of income. This paper presents an overview of key concepts and approaches to health sector reform in developing countries. Reform implies sustained, purposeful, and fundamental changes in the health sector. While it is difficult to define precisely what constitutes a true reform, there is widespread consensus that reform is a process of change involving the what, who, and how of health sector action. Health is increasingly included as an important goal of national development. It can make development more sustainable. The paper outlines some general and specific health sector reform strategies that can contribute to sustainable development for countries at all levels of income, although the strategies will differ in content and emphasis. Health sector reform should be based on an holistic view of the health sector. The paper presents two frameworks to aid in reform design: one highlighting the linkages between different institutional actors in the health sector; the second addressing linkages across different functional areas of reform action. In order to develop and carry out reform, information and analysis is needed. A variety of practical tools now available for this purpose are discussed, encompassing all the different areas of action. While tool development should continue, reform proponents already have much to work with. Given global interest, the importance of health sector reform in development strategies, and significant existing knowledge and experience, country level analysis and action should proceed vigorously.