Health systems internationally are attempting to address the issue of how to monitor and regulate quality of care in order to maintain and drive up standards. In the UK, policy initiatives focused upon revalidation for clinicians and incident reporting raise questions around how best to feedback and use data to support improvement at professional level. Considerable research has been undertaken to outline the processes by which valid, reliable and useful quality indicators can be defined. The evidence base for how to maximise the influence of feedback on professional behaviour, however, remains heterogeneous. Greater research effort needs to be devoted to understanding the underlying mechanisms through which feedback achieves its goals. This PhD therefore aims to describe and investigate the characteristics and mechanisms by which feedback influences professional behaviour in healthcare. Two perspectives are selected to provide alternative viewpoints. The first is focussed upon personalised feedback interventions in anaesthesia and the second centres around organisational level feedback from incident reporting systems. Within the thesis case study feedback interventions from each of the two perspectives are investigated and evaluated using a mixed methods approach. Qualitative analysis draws upon inductive and theoretically informed deductive reasoning whilst both descriptive and inferential statistics are employed to explore survey data. Participants include consultant anaesthetists, safety science experts and risk managers, among others. Synthesis of results demonstrates that providing feedback is a complex, social, quality improvement intervention. Its influence on professional behaviour is a multifaceted interaction between design characteristics/pre-conditions, psychological processes and intermediary outputs. These mechanisms can be better understood from a sociotechnical perspective drawing upon the fields of psychology, human factors, organisational studies and health services research. This thesis presents an integrative model for understanding the mechanisms through which feedback influences professional behaviour in healthcare.