BACKGROUND: Globally, there is a growing interest in explicit healthcare priority-setting processes such as Health Technology Assessment (HTA) to inform resource allocation decisions within the health sector. However, few studies have examined the policy process, implementation, and institutionalization of explicit healthcare priority-setting at the macro (national)-level in low and lower-middle income countries. This thesis critically examined the factors that influenced the: - a) policy process for the formulation of the policy on the Health Benefits Package Advisory Panel (HBPAP), b) implementation of HBPAP’s healthcare priority-setting process; and c) institutionalization of HTA as an approach for explicit healthcare priority-setting in Kenya. STUDY METHODS: I conducted three qualitative case studies related to the three sub-studies of this PhD namely the policy process, implementation, and institutionalization of explicit healthcare priority-setting in Kenya. I collected data using in-depth interviews (n=70) and document reviews. I analyzed these data thematically. Both data collection and analysis were informed by Kingdon’s theory, Barasa et al., evaluative framework, and my own framework (developed from a scoping literature review) as appropriate to the three sub-studies. FINDINGS: The policy process that led to the gazettement of the HBPAP policy idea was influenced by technocrats who not only identified the issues of fragmented and implicit healthcare priority-setting processes but also developed the policy solution of establishing an independent expert panel and acted as policy entrepreneurs when a policy window opened following the political prioritization of universal health coverage (UHC). The implementation of HBPAP’s healthcare priority-setting process partially met the normative procedural and outcome conditions of a “good” healthcare priority-setting process. While HBPAP had put in place “good” procedural practices such as use of evidence, transparency, stakeholder involvement, stakeholder empowerment, appeals and enforcement, their fulfilment was undermined by internal factors such as short timelines and limited financial resources, and external factors such as limited data quality and availability, limited technical expertise and/ or experience in healthcare priority-setting among external stakeholders, and stakeholders’ interests. Lastly, institutionalization of HTA as an approach for explicit healthcare priority-setting in Kenya was influenced by factors that both supported and constrained the process. The supportive factors included presence of: - organizational structures for HTA; short-term capacity-building activities; awareness creation initiatives; policymakers’ interests in UHC and optimal allocation of resources; technocrats’ interests in evidence-based processes; and international collaboration. On the other hand, factors that constrained institutionalization included: - limited availability of financial, information, and skilled human resources; lack of HTA guidelines and decision-making frameworks; limited availability of long-term capacity-building activities; limited HTA awareness among subnational stakeholders; and industries’ interests in safeguarding their revenue. CONCLUSIONS: The policy process, implementation, and institutionalization of explicit healthcare priority-setting in Kenya occurred in political environments characterized by varying stakeholders’ interests and other contextual factors related to resource constraints that both supported and constrained the processes. This study shows that proponents of policy ideas on explicit healthcare priority-setting should not only examine which policymakers may be most supportive of these ideas but also identify synergies of interest that could be explored to facilitate uptake of these ideas in the health system. It also shows that policymakers can support implementation of explicit healthcare priority-setting processes by developing strategies to manage internal and external factors that might undermine fulfilment of normative procedural and outcome conditions. Lastly, it shows that policymakers can nurture and sustain institutionalization of HTA as an explicit approach for health care priority-setting in Kenya by adopting a systemic approach that not only ensures availability of organizational resources; legislation & policies; learning & advocacy; and collaborative support but also identifies and aligns supportive stakeholders’ interests.