Evidence, in its multiple forms, is often perceived as playing key roles in public health policy development, although how and why evidence is used and when, despite a wide range of research on the subject, is less clear. This thesis – the final component of the professional doctorate programme known as the Doctor of Public Health (DrPH), which is intended for leaders and future leaders in public health policy and practice – looked at the policy development processes of two different global malaria preventive treatment policies produced by the World Health Organization (WHO) known as ‘Intermittent Preventive Treatment in infants’ (IPTi) and ‘Seasonal Malaria Chemoprevention’ (SMC). The aim of the DrPH research was to better understand the influences on the use of evidence in policy making in organisations such as the WHO, using a case study of the WHO’s malaria department – the Global Malaria Programme (WHO-GMP). Specifically, the thesis objectives are to: (a) explore the factors that influenced the consideration of particular evidence at WHO-GMP, i.e. determine what was considered ‘good evidence’ for policy (and why) in the case of IPTi and SMC; and (b) examine how factors associated with the policy process influenced eventual policy outcomes at WHO-GMP, i.e. determine what was considered ‘good use of evidence’ for policy (and why) in the case of IPTi and SMC. A more holistic understanding of what influences the use of evidence in policy making may help shed more light on the complexity of evidence use, and may help, in multidimensional ways, to increase and improve evidence use, which is the goal of many public health organisations, including the WHO. By comparing the policy development processes for IPTi compared to SMC, the findings showed that forms of ‘good evidence’ often held up as high quality in terms of technical considerations, though important, were not sufficient to ensure universal agreement and uptake of recommendations, even within a highly technocratic body such as WHO-GMP. An analysis of 29 key informant interviews found that the perceived relevance of evidence to the policy question being asked mattered to expert actors, and that they also retained a concern over the legitimacy of the process by which technical evidence was brought to bear in the policy development process. Cash and colleagues’ (2003) findings from the field of sustainable development, that evidence must be credible, salient, and legitimate, to be accepted by the public, appears to equally apply within this evidence advisory body within WHO. While the WHO has principally focused on technical criteria for evidence inclusion in its policy development processes, this study suggests that the design and functionality of its advisory bodies must also enable transparent, responsive, and credible processes of evidence review to ensure that these bodies are effective in producing advice that engenders change in policy and practice. The findings from this thesis contribute to the public health policy literature on evidence use in policy making, and will be of interest to scholars of health policy as well as public health policy makers and practitioners.