The neutrality of evaluation processes has been widely discussed in both the academic and practitioner literature. The abstraction of assessment mechanisms from the reality of public policy arguably seems naïve and disconnected from the actual role of evaluation. It is in exactly this context that this thesis explores the politics of evaluation in terms of both an internal process and an external procedure within accountability frameworks. By focusing on the political nature of evaluation in healthcare in Mexico and the United Kingdom this thesis sheds new light on the complex relationships and inter-dependencies that dominate the architecture of modern governance. The core finding of the research presented in this thesis is that the hidden politics of evaluation matters because of the way in which the institutional framework provides actors with spaces of discretion that allow them to influence the process and outcomes of evaluation. This finding, and the research that underpins it, adds to our understanding in terms of the potential gap between what might make ‘good policy’, as opposed to what might make ‘good politics.