There are three domains of expertise required for consistently effective performance in emergency medicine (EM): procedural, affective, and cognitive. Most of the activity is performed in the cognitive domain. Studies in the cognitive sciences have focused on a number of common and predictable biases in the thinking process, many of which are relevant to the practice of EM. It is important to understand these biases and how they might influence clinical decision-making behavior. Among the specialities, EM provides a unique clinical milieu of inconstancy, uncertainty, variety, and complexity. Injury and illness are seen within narrow time windows, often under pressured ambient conditions. These operating characteristics force practitioners to adopt a distinctive blend of thinking strategies. Principal among them is the use of heuristics, a form of abbreviated thinking that often leads to successful outcomes but that occasionally may result in error. A number of opportunities exist to overcome interdisciplinary, linguistic, and other historical obstacles to develop a sound approach to understanding how we think in EM. This will lead to a better awareness of our cognitive processes, an improved capacity to teach effectively about cognitive strategies, and, ultimately, the minimization or avoidance of clinical error.