OBJECTIVES: With the increasing demands for health care from rapid medical technological advancement, the Taiwan National Health Insurance (TNHI) demands for the development of systematic, transparent, and participatory processes for selection of new health interventions to be included into the NHI Benefits Schedule (NHIBS). Though evaluation of applications from the medical profession for the listing of new health intervention on the NHIBS is recognized as a democratic decision making, its fairness and legitimacy have not been assessed. This study aimed to assess the fairness and legitimacy of decisions in the priority setting process for new health interventions into the NHIBS. METHODS: Both the four conditions of accountability for reasonableness (Daniels and Sabin,2002):relevance, publicity, appeals, and enforcement and the four steps of the trans-disciplinary model operational goals for priority setting in health care(Gibson et al, 2002):reasonableness, transparency, responsiveness, and accountability are used to assess the fairness and legitimacy of the priority setting decisions. The data for analysis was from public documents, related audit reports, literature review, observations from the meetings of the NHI Benefits Negotiation responsible for recommending new technologies for the NHIBS and interviews with the meeting participators. RESULTS: The Taiwan process for updating the NHIBS lacks the appeals and enforcement conditions, and only partially follows the relevance and publicity conditions. Only the reasonableness and transparency steps of the trans-disciplinary model are partially fulfilled, but the priority setting process does not satisfy responsiveness and accountability. CONCLUSIONS: The fairness and legitimacy of the priority-setting decision mechanism have not been established. The lack of personnel engaged in health technology assessment and the desire for early adoption of new technologies are an obstacle to achieving these conditions. Comprehensive changes in the priority-setting process should be made in order to increase its acceptability among the different stakeholders.