The pace and breadth of health reforms point to the need for a comparative methodology to support shared learning from country experiences. A common understanding of health reforms is a first prerequisite for comparative research. Dimensions characterising content, sequence, process, purpose and scope of policy change are identified on the basis of a literature review. Reforms can have a gradual build up, starting with piecemeal policy changes that can be eventually integrated to enhance their benefits. Comprehensive reforms can be defined as policy formulation and implementation that comprises the systemic, programmatic, organisational and instrumental policy levels through explicit strategies sustained in well-documented experiences and theories and implemented with the support of a specialised agency with consensus-building capacity. A minimum-data set is proposed on the basis of an extensive literature review to support the comparability of health reform case studies and descriptions. Its components are: the current health system, its background and context, the reform rationale, the specific proposals, political actors and processes, achievements and limitations, and lastly the reform's wider impact. Case studies can be compared historically, through particularistic comparisons, using ideal types and by means of exemplars. The advantages and limitation of each method are analysed as well as how they can be combined to frame the research questions and minimise resources. Finally, the International Clearinghouse for Health System Reform Initiatives is described as an instrument to disseminate comparative research and analysis in support of shared learning.