Background. Most countries that have based their healthcare systems on primary care enjoy better population health, lower health disparities, more equitable access to care, and lower costs. Iranian primary health care (PHC) has achieved population health indices similar to that of the best in the region during the past two decades. Despite this, the system showed itself to be both inadequate in meeting the evolving health needs of the population and unaffordable by many. To address these shortages, in 2005 it was decided to implement a new system, called family medicine (FM), together with Behbar (rural insurance for all) in rural areas and in urban areas of less than 20,000 population. The aim of this thesis was to identify facilitators of and barriers to the implementation of FM in Iran. Methods. Qualitative methods were used, particularly individual semi-structured interviews with stakeholders at three levels: national (19 interviews), provincial (9), and local (43). In addition, three focus groups, document analysis, and observations in health centres were used. The framework approach was employed as the main method for analysis, while remaining open to accommodate emerging themes. The analysis was based on a modified fourfold framework consist of administration, bargaining, interpretation and institutional structuring components, originally introduced by Harrison (2004). Results. The study revealed four interdependent factors that influenced implementation: aspects of the policy; the existing environment; the experience of implementation; and attitudes and perceptions of local practitioners and the public. Making the policy in the 'organized anarchies' of the health system, where ambiguity is prevalent, few people involved and imposing it on others was at the heart of problems with implementation. The policy that was conceptually welcomed because of its innovation and incentive for cooperation, was badly put into practice. The core barrier was the merger of two diverse policies, implemented concurrently by two hostile organizations (MOH & MIO). Conclusions. The thesis revealed the dynamic model of health policy analysis. The policy was essentially adopted on the basis of idealistic views rather than a real solution to existing problems. Implementation was an attempt by two organizations with different aims. Despite some efforts to reduce practical difficulties, the underlying divergence between Behbar and FM was too fundamental to be overcome. Parliament's attempt to separate the purchaser from the provider resulted in great mistrust between the two and to some extent undermined the essence of FM.