The concepts of intervention fidelity and how they can influence the results of clinical trials. The focus of clinical trials is typically interventions' efficacy, or whether they attain their desired outcomes. Comparatively less attention is focused on understanding how or why interventions succeed, or fail to attain, those outcomes. This may be particularly important in trials of complex interventions such as surgery or physiotherapy, which are multifaceted and often tailored to individual participants, providers, or settings, increasing the potential for variations in intervention delivery and effects. The correspondence between the intervention that was planned and what was actually delivered in a trial is the intervention's fidelity. In this presentation, we will discuss intervention fidelity and concepts related to it such as participant adherence (the actions of patients and participants in a clinical trial), and how they can influence the results of a clinical trial, as well as our level of confidence in the results of published trials. A checklist for assessing intervention fidelity in clinical trial publications will also be presented. Dr. Paez is a post-doctoral fellow at the Sleep, Cognition, and Neuroimaging Laboratory at Concordia University, Montreal, an Assistant Professor of Medicine and Clinical Skills Training, NAPCA, and a Senior Lecturer at the Bouvé College of Health Sciences, Northeastern University, Boston. He obtained an MSc and DPhil in Evidence-based Healthcare from the University of Oxford, UK, a PhD in Health and Exercise Science from Concordia University, and doctoral degree in Physiotherapy from Northeastern University, Boston. Dr. Paez is also a visiting scholar and council member of the IDEAL Collaboration, Nuffield Department of Surgical Sciences, University of Oxford, which focuses on improving innovation and evidence for complex interventions in healthcare, such as Surgery and Rehabilitation.