Background: Emergency physicians (EPs) can choose from several evidence-based pathways to diagnose pulmonary embolism (PE), however literature suggests that EPs frequently use computer tomography (CT) scanning as a stand-alone test for PE. This is a program of research to improve adherence to evidence-based PE diagnosis in the emergency department (ED). Aim Statement: To create a novel approach to PE diagnosis in the ED based on a framework explaining EP diagnostic PE behaviour and barriers to using evidence-based PE testing. Measures & Design: We conducted two types of qualitative interviews: 1). EPs in 5 Canadian cities watched videos of 2 simulated cases and then explained how they would test the patient. 2). Semi-structured EP interviews using the theoretical domains framework (TDF). The results of our analyses informed the construction of an explanatory framework for common EP diagnostic PE behaviours. Barriers to evidence-based behaviour were classified into domains. A Canadian EP expert group reviewed these results along with the existing evidence on ED PE diagnostic implementation. We developed a new approach to diagnosis of PE in the ED which addresses each of our domains. Evaluation/Results: We conducted 71 interviews. We identified 4 domains, each addressed in our pathway. ‘PE in a mythical and deadly beast’ PE kills and can masquerade so EPs look for PE in places where it does not exist and are rewarded for ‘over-testing’. Response: Creating a departmental conversation about missing PE, talking about the facts, busting the myths. EP feedback on PE testing including positive rate. ‘The end goal is CTPE’ PE creates anxiety for EPs and ordering a CTPE hands over responsibility to the radiologist. Response: A departmental protocol for PE testing which starts with D-dimer for every patient. Shifting focus to ruling out PE with D-dimer. Protocol is automated once initiated by EP. ‘PERC eases anxiety’ PERC is documented when it is negative and allows EP to stop. Response: EPs can choose to use and document PERC. ‘No-one has been fighting for the Wells score’ Poor understanding of purpose and function. Often at odds to Gestalt. Response: Protocol does not use Wells score. Discussion/Impact: We have developed a new diagnostic PE pathway which addresses current barriers to evidence-based practice which we will evaluate further.