In 2001, Thailand introduced the Universal Coverage of Health Care Policy (UC) very rapidly after the new government came to power. The policy aims to entitle all citizens to health care and includes health system reforms to achieve equity, efficiency, and accountability. The overall question this thesis asks is how did this policy come about, and how likely is it that the policy will achieve its goals? Literature suggests that understanding the policy process is as important as assessing the content of particular policies when judging policy outcomes. By using an analytical framework to explore four elements: context, actors, process, and content, this thesis aims to generate general understanding of the UC policy process, and to use this analysis to assess implementation. It starts by addressing how and why universal coverage, which had long been discussed in Thailand, got on to the policy agenda in 2001, and then explores how the policy was formulated nationally. It goes on to look at implementation in one province, examining the inter-relationships between provincial, district and community facilities. Data were gathered from key informant interviews, document and media analysis, and group discussion with villagers. The analysis suggests that Thailand's democratization, created new actors in health policymaking processes which had long been under control of bureaucrats and professionals. The 1997 Constitution encouraged a more pluralistic political system. Universal access to health was advocated by a group of non-government organizations who pushed to get UC through legislation and announced their campaign a few months before the 2001 election. NGO interest was paralleled by a political party campaign, announced in 2000 by the Thai-Rak Thai Party, and implemented as UC when the Party came to power. UC was picked up because it was seen as legitimate, feasible under the existing infrastructure and government budget, and also congruent with the reform intention of the political party. Once it became the government in 2001, an important factor in early policy formulation was the extent to which national research provided evidence to support the policy. The research community was tightly-knit and concentrated in medical-related professions. One member of this policy community played an important role as a policy entrepreneur. This policy community continued to support evidence for debates in policy-making during both policy formulation and implementation. The implementation process was a top-down process; however, there were some spaces for street level bureaucrats to adapt decisions to fit their context. Implementation started through the extension of insurance coverage in four phases under the execution of the Ministry of Public Health. Private providers were only minimally involved in these formulation and implementation phases. The UC policy in 2001-2 was characterised by clear policy goals, limited participation, strong institutional capacity, and very rapid implementation - all factors which anticipated success of the policy. However, the complex technical features of the policy and the big change in system reform were a brake on success. One of the implementation problems was the mobilization of human resources, especially where bureaucrats were resistant to change. It seems that the implementation of the UC policy in Thailand reflected both managerial as well as political problems. Given the findings of this study, policy monitoring should pay attention to political as well as technical assessment.