The book covers various scenarios when errors, biases and systemic barriers prevail in emergency medicine, discusses their impact, and then offers solutions to mitigate their undesired outcomes. The process of clinical reasoning in emergency medicine is a complex exercise in cognition, judgment and problem-solving that is prone to mistakes. The book presents various cases written by a team of emergency specialists and trainees in an engaging format that is helpful for the practicing and teaching emergency doctor and trainees. The book discusses 51 different types of biases and errors with clinical cases, and knowledge of strategies to mitigate them-a concept known as 'cognitive debiasing' that has the potential to reduce diagnostic error, and therefore, morbidity and mortality. It aims to help the readers during assessment of patients in the emergency department. Each chapter includes 4 cases illustrating the bias, error or barrier discussed, followed by a potential solution. This book helps in polishing the thinking and behavior of the readers so to potentially enhance their clinical competence in emergency department.