Crowding is an increasingly common occurrence in hospital-based emergency departments (EDs) across the globe. This 2-article series offers an ethical and policy analysis of ED crowding. Part 1 begins with a discussion of terms used to describe this situation and proposes that the term "crowding" be preferred to "overcrowding." The article discusses definitions, measures, and causes of ED crowding and concludes that the inability to transfer emergency patients to inpatient beds and resultant boarding of admitted patients in the ED are among the root causes of ED crowding. Finally, the article identifies and describes a variety of adverse moral consequences of ED crowding, including increased risks of harm to patients, delays in providing needed care, compromised privacy and confidentiality, impaired communication, and diminished access to care. Part 2 of the series examines barriers to resolving the problem of ED crowding and strategies proposed to overcome those barriers.