© Cambridge University Press 2017. Introduction In recent years, there has been an increased emphasis placed on the importance of patient engagement in both chronic and acute care. Patient engagement can be broadly defined as active patient involvement in their healthcare to strengthen their influence on medical decisions and behaviors. A key component of patient engagement is shared decision-making (SDM). SDM is defined as a process by which patients and providers consider outcome probabilities and patient preferences and reach a healthcare decision based on mutual agreement. An SDM approach to clinical decisions in the emergency department (ED) is a reliable way to have the patient's voice heard with regard to their values, preferences, and unique circumstances. In this chapter, we describe concepts underlying SDM, review the existing literature on patient decision aids and SDM in the ED setting, and offer three clinical vignettes to illustrate the process of SDM in emergency care. What Is Shared Decision-Making? SDM is an approach in which clinicians actively bring the patient's voice into the medical encounter. Although the patient's role has classically been relegated to providing a history of the present illness and answering specific clinical questions, patients can have a more active role through asking questions, voicing concerns, and expressing values and preferences. Charles, Gafni, and Whelan described a conceptual model of SDM in the context of medical encounters for potentially life-threatening chronic conditions. They proposed four key characteristics of SDM: (1) at least two participants must be involved – physician and patient (or surrogate); (2) both parties share information; (3) both parties build consensus regarding the patient's preferred treatment; and (4) a mutual agreement is reached on the treatment to pursue. They describe a spectrum from paternalistic, physician-directed decision-making to fully informed, patient-directed decision-making, with SDM lying in the middle. The purported benefits of such an approach include increased patient satisfaction, increased adherence to treatment, and improved functional status. SDM is also appropriate for ED care. All ED encounters entail clinical decisions, be they diagnostic, therapeutic, or dispositional (i.e., whether the patient is admitted or discharged from the ED).