Greece has enacted three major health care reforms since the National Health System (NHS) was established in 1983. These reforms were designed to improve the system's ability to realize its founding principles of equity and efficiency in the delivery and financing of health services. This article presents an early report of ongoing doctoral research that aims to examine the relative influence of medical professional organizations versus other interests on these reforms. The article outlines three theoretical frameworks for understanding the health care system and the role of the medical profession within it in order to establish which best explains the nature and extent of health care reform. These frameworks are: sociological theories of professions; historical institutionalism; and structural interest theory.