Objective: Public trust in health systems is pivotal for their effective and efficient functioning. In particular, public trust is essential for personal data use, as demonstrated in debates in many countries, for example, about whether data from COVID-19 contact tracing apps should be pooled or remain on individuals’ smartphones. Low levels of public trust pose a risk not only to health system legitimacy but can also harm population health. Methods: Synthesising our previous qualitative and theoretical research in the English National Health Service which enabled us to conceptualise the nature of public trust in health systems, we present guiding principles designed to rebuild public trust, if lost, and to maintain high levels of public trust in personal data use within the health system, if not. Results: To build public trust, health system actors need to not rush trust building; engage with the public; keep the public safe; offer autonomy to the public; plan for diverse trust relationships; recognise that trust is shaped by both emotion and rational thought; represent the public interest; and work towards realising a net benefit for the health system and the public. Conclusions: Beyond policymakers and government officials, the guiding principles address a wide range of actors within health systems so that they can work collectively to build public trust. The guiding principles can be used to inform policymaking in health and health care and to analyse the performance of different governments to see if those governments that operate in greater conformity with the guiding principles perform better. This research is published in: Gille F, Smith S, Mays N. Evidence-based guiding principles to build public trust in personal data use in health systems. DIGITAL HEALTH. 2022;8. doi:10.1177/20552076221111947 [1] Links: ------[1] https://doi.org/10.1177/20552076221111947