Emergency department observation units (EDOUs) provide an essential model of care to address emergency department crowding, preventable hospital admissions, and rising health-care costs through protocol-driven, short-term management of patients requiring further evaluation or treatment.This interim update to the 2013 American College of Emergency Physicians Policy Resource and Education Paper reviews the current state of observation medicine, highlighting structural and staffing principles, professional billing models, and evolving applications across diverse clinical conditions, including geriatrics, toxicology, psychiatry, oncology, and chest pain.Recent developments in telehealth integration, pandemic surge response, and novel clinical pathways underscore the adaptability and high-value role of observation units within modern emergency care.By consolidating evidence-based practices and policy considerations, this paper emphasizes the continued importance of EDOUs in improving efficiency, outcomes, and cost-effectiveness while outlining key directions for future research and implementation. CONCEPTS, PRINCIPLES, AND DEFINITIONSHospitals and emergency departments (EDs) continue to face the challenges of escalating health-care costs, resource provisioning and utilization, minimizing avoidable admissions, and overcrowding.Hospitals use emergency department observation units (EDOUs) to address these issues.Research in this setting has increased in recent years, leading to a better
Caspers et al. (Fri,) studied this question.