This thesis investigates the emergence and significance of the phenomenon termed the contemporary promise of quality in healthcare. This phenomenon is shown to be part and product of a historically extraordinary set of movements that have remade quality in a form that is explicit, calculable, expressible as accounting numbers, and amenable to management ideas and ideals. It is also shown to be closely inter-twined with the emergence of a distinct way of contemplating and undertaking reform of the healthcare sector; a politically attractive means of continually responding to failures by calling for the import of the newest improvement interventions. This thesis documents the historical specificity of these movements and tracks their international reach. It also investigates what the phenomenon entails for healthcare systems, organizations, professionals and patients as it is variously operationalized. Investigating the USA and UK health reforms, and experiences with reform, in detail, this thesis shows that this phenomenon is closely connected with a movement of care activities ‘onto the balance sheet’ and toward representational activities rather than the activities that historically constituted the practices of caring. It also shows this phenomenon to be closely connected with changing forms of expertise, knowledge and professionalism in healthcare. It identifies, for example, the emergence of knowledge about managing experiences, and a certain style of engaging with numbers and acting in an outwardly entrepreneurial way, as closely intertwined with this movement. This thesis as a whole, by attending to the wider movements of which quality and its calculations are part and product, contributes to our understanding of accounting, quality, healthcare, professionalism, and government reforms. It shows the way that a calculable quality emerged and moved between time and place, and in the process reconfigured the very nature of policy-making and caring.