To many, the expression ‘health system reform’ brings to mind a particular set of measures widely adopted during the 1990s in order to deal with a particular problem: increased reliance on private sector institutions and operating procedures in order to improve efficiency. But in principle, the expression ‘health system reform’ is a general one, applied to a broad range of policy measures designed to deal with an equally broad range of problems. According to one standard definition, for example, health sector reform can be defined as ‘sustained, purposeful change to improve the efficiency, equity, and effectiveness of the health sector.’ 1 Adoption of a broader definition provides an opportunity to move beyond the current narrow debate over whether the particular reform measures of the past have helped or harmed the poor, to a broader look at the reform measures required to benefit the poor in the future. Such a look is badly needed. For a rapidly-growing body of evidence points to large differences between the poor and better-off not only with respect to health status and the use of private health services, but also with respect to the use of government services, including services widely promoted because of their anticipated relevance for the poor. This evidence points to a clear need for a new wave of major equity-oriented health sector reforms, conceived and executed with even more passion and determination than the efficiencydirected reforms of the 1990s. The objective: to increase the efficiency and effectiveness with which health systems reach the poor and disadvantaged, thereby alleviating current inequities in health service use and contributing to lessened differences in health status. The passages that follow will seek to stimulate further thought about how to achieve such reforms by presenting three arguments. The first is that significant reforms will require changes that are far deeper than commonly recognized in policy circles. The second is that current movement toward debt relief in poor countries is creating a climate potentially more favourable to such deeper changes than the climate of the recent past. The third is that epidemiological and health systems researchers can best help equity-oriented health policy makers take advantage of the present climate by developing an evidence base concerning intervention options for reaching the poor effectively.