Application of normalisation process theory in understanding implementation processes in primary care settings in the UK: A systematic review HuddlestoneL TurnerJ EborallH HudsonN DaviesM MartinG 2020 Background: Normalisation Process Theory (NPT) provides a framework to understand how interventions are implemented, embedded, and integrated in healthcare settings. Previous reviews of published literature have examined the application of NPT across international healthcare and reports its benefits. However, given the distinctive clinical function, organisational arrangements and the increasing management of people with a wide variety of conditions in primary care settings in the United Kingdom, it is important to understand how and why authors utilise and reflect on NPT in such settings to inform and evaluate implementation processes. Methods: A systematic review of peer-reviewed literature using NPT in primary care settings in the United Kingdom (UK) was conducted. Eight electronic databases were searched using replicable methods to identify articles published between January 2012 and April 2018. Data were analysed using a framework approach. Results: Thirty-one articles met the inclusion criteria. Researchers utilised NPT to explore the implementation of interventions, targeting a wide range of health services and conditions, within primary care settings in the UK. NPT was mostly applied qualitatively; however, a small number of researchers have moved towards mixed and quantitative methods. Some variation was observed in the use of NPT constructs and sub-constructs, and whether and how researchers undertook modification to make them more relevant to the implementation process and multiple stakeholder perspectives. Conclusion: NPT provides a flexible framework for the development and evaluation of complex healthcare interventions in UK primary care settings. This review updates the literature on NPT use and indicates that its application is well suited to these environments, particularly in supporting patients with long-term conditions and co-morbidities. We recommend future research explores the receipt of interventions by multiple stakeholders and suggest that authors reflect on justifications for using NPT in their reporting.