Working in an emergency department as a psychiatrist or mental health clinician requires an ability to gain a patient's rapport, establish a differential diagnosis, assess risk and make disposition decisions in a fast-paced and potentially chaotic setting. Patients may be medically ill, agitated, intoxicated, or suicidal, and resources for treatment may be difficult to access. A Case-Based Approach to Emergency Psychiatry provides the emergency department clinician with vivid and complex cases, discussed by psychiatrists who work daily in the emergency setting, that illustrate basic principles of assessment, diagnosis and treatment. These challenging and complex cases are based on the years of experience of the authors combined with current evidence-based practices and discussion. Risk assessment, psychosis, mood disorder, substance abuse, ethics, forensic issues, and personality disorders are discussed, along with child and adolescent, geriatric, and developmental disabilities. Special attention is also paid to alternatives to inpatient care, short-term crisis intervention, and the interface between medical and psychiatric illnesses. The case-based format allows the authors to link aspects of the clinical presentation to discussion and literature review in a memorable and compelling format.