What can we learn from international comparisons of health systems and health system reform?

Most commonly, lessons derived from comparisons of international health sec tor reform can only be generalized in a limited way to similar countries. H owever, there is little guidance as to what constitutes "similarity" in thi s respect. We propose that a framework for assessing similarity could be de rived from the performance of individual policies in different contexts, an d from the cause and effect processes related to the policies. We demonstra te this process by considering research evidence in the "public-private mix ", and propose variables for an initial framework that we believe determine private involvement in the public health sector. The most influential mode l of public leadership places the private role in a contracting framework. Research in countries that have adopted this model suggests an additional l ist of variables to add to the framework. The variables can be grouped unde r the headings "demand factors", "supply factors", and "strength of the pub lic sector". These illustrate the nature of a framework that could emerge, and which would help countries aiming to learn from international experienc e.